Patterns of primary productivity and biomass in a coastal upwelling region

NASA Astrophysics Data System (ADS)

Small, Lawrence F.; Menzies, David W.

1981-02-01

Average distributions of chlorophyll α during upwelling in areas of smooth bathymetry off Oregon have been computed from historical data. Chlorophyll concentrations in cross-shelf sections over the Oregon continental shelf (44°40'N) were similar to those in cross-shelf sections off northwest Africa during JOINT-1 studies but differed from those in similar sections over an adjacent narrow region of the Oregon shelf (44°55'N to 45°12'N). The fact that larger concentration differences can occur along short sections of one coastline than between upwelling regions half a world apart bears on the time and space scales of sampling and might have bearing on the support and distributions of other trophic levels. Relationships between the local winds and the broader-scale BAKUN (1975) upwelling indices were used to classify various phytoplankton biomass and primary productivity distributions according to whether they were in strong upwelling steady state, weak upwelling steady state, or one of two transition states. The upwelling steady state conforms to the 'upwelling event' scale (about 3 to 10 days) of WALSH, WHITLEDGE, KELLEY, HUNTSMAN and PILLSBURY (1977) and the transition state of approximately one-day duration might specify the critical scale for driving the upwelling off Oregon. Under strong steady-state upwelling in early summer a single band of high primary productivity and biomass develops in the surface layer parallel to the bottom contours, but under similar upwelling conditions in later summer a two-celled zonal circulation occurs and two parallel bands develop. Our strong upwelling distributions are discussed in light of current models of the Oregon upwelling system. Maintenance of biological properties through time in the upwelling bands is also discussed. Under weak steady-state upwelling the primary productivity and biomass bands are farther inshore or immediately against the coast. Productivity in the weak upwelling bands can be twice that of the strong upwelling bands and often 20 times that in surrounding water. Under transient conditions in which the local winds are favorable for strong upwelling but the slower-responding Bakun index indicates weak upwelling, chlorophyll distributions change within a day to resemble distributions during strong steady-state upwelling. Under transient conditions in which the local winds weaken dramatically but the Bakun index still indicates strong upwelling, chlorophyll concentrations are high and widely distributed throughout the upwelling region.

Response of the Benguela upwelling systems to spatial variations in the wind stress

NASA Astrophysics Data System (ADS)

Fennel, Wolfgang; Junker, Tim; Schmidt, Martin; Mohrholz, Volker

2012-08-01

In this paper we combine field observations, numerical modeling and an idealized analytical theory to study some features of the Benguela upwelling system. The current system can be established through a combination of observations and realistic simulations with an advanced numerical model. The poleward undercurrent below the equator-ward coastal jet is often found as a countercurrent that reaches the sea surface seaward of the coastal jet. The coastal band of cold upwelled water appears to broaden from south to north and at the northern edge of the wind band an offshore flow is often detected, which deflects the coastal Angola current to the west. These features can be explained and understood with an idealized analytical model forced by a spatially variable wind. A crucial role is played by the wind stress curl, which shapes the oceanic response through Ekman-pumping. The interplay of the curl driven effects and the coastal Ekman upwelling together with the coastal jet, Kelvin waves, and the undercurrent is the key to understand the formation of the three-dimensional circulation patterns in the Benguela system. While the numerical model is based on the full set of primitive equations, realistic topography and forcing, the analytic model uses a linear, flat-bottomed f-plane ocean, where the coast is a straight wall and the forcing is represented by an alongshore band of dome-shaped wind stress. Although the analytical model is highly idealized it is very useful to grasp the basic mechanisms leading to the response patterns.

Climate change and ocean deoxygenation within intensified surface-driven upwelling circulations.

PubMed

Bakun, Andrew

2017-09-13

Ocean deoxygenation often takes place in proximity to zones of intense upwelling. Associated concerns about amplified ocean deoxygenation arise from an arguable likelihood that coastal upwelling systems in the world's oceans may further intensify as anthropogenic climate change proceeds. Comparative examples discussed include the uniquely intense seasonal Somali Current upwelling, the massive upwelling that occurs quasi-continuously off Namibia and the recently appearing and now annually recurring 'dead zone' off the US State of Oregon. The evident 'transience' in causal dynamics off Oregon is somewhat mirrored in an interannual-scale intermittence in eruptions of anaerobically formed noxious gases off Namibia. A mechanistic scheme draws the three examples towards a common context in which, in addition to the obvious but politically problematic remedy of actually reducing 'greenhouse' gas emissions, the potentially manageable abundance of strongly swimming, finely gill raker-meshed small pelagic fish emerges as a plausible regulating factor.This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'. © 2017 The Author(s).

Coastal upwelling south of Madagascar: Temporal and spatial variability

NASA Astrophysics Data System (ADS)

Ramanantsoa, Juliano D.; Krug, M.; Penven, P.; Rouault, M.; Gula, J.

2018-02-01

Madagascar's southern coastal marine zone is a region of high biological productivity which supports a wide range of marine ecosystems, including fisheries. This high biological productivity is attributed to coastal upwelling. This paper provides new insights on the structure, variability and drivers of the coastal upwelling south of Madagascar. Satellite remote sensing is used to characterize the spatial extent and strength of the coastal upwelling. A front detection algorithm is applied to thirteen years of Multi-scale Ultra-high Resolution (MUR) Sea Surface Temperatures (SST) and an upwelling index is calculated. The influence of winds and ocean currents as drivers of the upwelling is investigated using satellite, in-situ observations, and a numerical model. Results reveal the presence of two well-defined upwelling cells. The first cell (Core 1) is located in the southeastern corner of Madagascar, and the second cell (Core 2) is west of the southern tip of Madagascar. These two cores are characterized by different seasonal variability, different intensities, different upwelled water mass origins, and distinct forcing mechanisms. Core 1 is associated with a dynamical upwelling forced by the detachment of the East Madagascar Current (EMC), which is reinforced by upwelling favourable winds. Core 2 appears to be primarily forced by upwelling favourable winds, but is also influenced by a poleward eastern boundary flow coming from the Mozambique Channel. The intrusion of Mozambique Channel warm waters could result in an asynchronicity in seasonality between upwelling surface signature and upwelling favourables winds.

The NAO Influence on the Early to Mid-Holocene North Atlantic Coastal Upwelling

NASA Astrophysics Data System (ADS)

Hernandez, A.; Cachão, M.; Sousa, P.; Trigo, R. M.; Freitas, M. C.

2017-12-01

Coastal upwelling regions yield some of the oceanic most productive ecosystems, being crucial for the worldwide social and economic development. Most upwelling systems, emerging cold nutrient-rich deep waters, are located in the eastern boundaries of the Atlantic and Pacific basins, and are driven by meridional wind fields parallel to the coastal shore. These winds are associated with the subsiding branch of the large-scale Anticyclonic high pressure systems that dominate the subtropical ocean basins, and therefore can be displaced or intensified within the context of past and future climate changes. However, the role of the current global warming influencing the coastal upwelling is, as yet, unclear. Therefore it is essential to derive a long-term perspective, beyond the era of instrumental measurements, to detect similar warm periods in the past that have triggered changes in the upwelling patterns. In this work, the upwelling dynamics in the Iberian North Atlantic margin during the early and mid-Holocene is reconstructed, using calcareous nannofossils from a decadally resolved estuarine sediment core located in southwestern Portugal. Results suggest that the coastal dynamics reflects changes in winds direction likely related to shifts in the NAO-like conditions. Furthermore, the reconstructed centennial-scale variations in the upwelling are synchronous with changes in solar irradiance, a major external forcing factor of the climate system that is known to exert influence in atmospheric circulation patterns. In addition, these proxy-based data interpretations are in agreement with wind field and solar irradiance simulation modelling for the mid-Holocene. Therefore, the conclusion that the solar activity via the NAO modulation controlled the North Atlantic upwelling of western Iberia during the early and mid-Holocene at decadal to centennial timescales can be derived. The financial support for attending this meeting was possible through FCT project UID/GEO/50019/2013 - Instituto Dom Luiz

Patterns and processes in the California Current System

NASA Astrophysics Data System (ADS)

Checkley, David M., Jr.; Barth, John A.

2009-12-01

The California Current System (CCS) is forced by the distribution of atmospheric pressure and associated winds in relation to the west coast of North America. In this paper, we begin with a simplified case of winds and a linear coast, then consider variability characteristic of the CCS, and conclude by considering future change. The CCS extends from the North Pacific Current (∼50°N) to off Baja California, Mexico (∼15-25°N) with a major discontinuity at Point Conception (34.5°N). Variation in atmospheric pressure affects winds and thus upwelling. Coastal, wind-driven upwelling results in nutrification and biological production and a southward coastal jet. Offshore, curl-driven upwelling results in a spatially large, productive habitat. The California Current flows equatorward and derives from the North Pacific Current and the coastal jet. Dominant modes of spatial and temporal variability in physical processes and biological responses are discussed. High surface production results in deep and bottom waters depleted in oxygen and enriched in carbon dioxide. Fishing has depleted demersal stocks more than pelagic stocks, and marine mammals, including whales, are recovering. Krill, squid, and micronekton are poorly known and merit study. Future climate change will differ from past change and thus prediction of the CCS requires an understanding of its dynamics. Of particular concern are changes in winds, stratification, and ocean chemistry.

Surface circulation and upwelling patterns around Sri Lanka

NASA Astrophysics Data System (ADS)

de Vos, A.; Pattiaratchi, C. B.; Wijeratne, E. M. S.

2013-09-01

Sri Lanka occupies a unique location within the equatorial belt in the northern Indian Ocean with the Arabian Sea on its western side and the Bay of Bengal on its eastern side. The region is characterised by bi-annually reversing monsoon winds resulting from seasonal differential heating and cooling of the continental land mass and the ocean. This study explored elements of the dynamics of the surface circulation and coastal upwelling in the waters around Sri Lanka using satellite imagery and the Regional Ocean Modelling System (ROMS) configured to the study region and forced with ECMWF interim data. The model was run for 2 yr to examine the seasonal and shorter term (∼10 days) variability. The results confirmed the presence of the reversing current system in response to the changing wind field: the eastward flowing Southwest Monsoon Current (SMC) during the Southwest (SW) monsoon transporting 11.5 Sv and the westward flowing Northeast Monsoon Current (NMC) transporting 9.5 Sv during the Northeast (NE) monsoon, respectively. A recirculation feature located to the east of Sri Lanka during the SW monsoon, the Sri Lanka Dome, is shown to result from the interaction between the SMC and the Island of Sri Lanka. Along the eastern and western coasts, during both monsoon periods, flow is southward converging along the south coast. During the SW monsoon the Island deflects the eastward flowing SMC southward whilst along the east coast the southward flow results from the Sri Lanka Dome recirculation. The major upwelling region, during both monsoon periods, is located along the south coast and is shown to be due to flow convergence and divergence associated with offshore transport of water. Higher surface chlorophyll concentrations were observed during the SW monsoon. The location of the flow convergence and hence the upwelling centre was dependent on the relative strengths of wind driven flow along the east and west coasts: during the SW (NE) monsoon the flow along the western (eastern) coast was stronger and hence the upwelling centre was shifted to the east (west). The presence of upwelling along the south coast during both monsoon periods may explain the blue whale (Balaenoptera musculus) aggregations in this region.

Analysis of the Inshore California Current System Off Central California Using Naval Oceanographic Office Survey Data from 1997 to 2002

DTIC Science & Technology

2012-09-01

toward the coast due to upwelling . Acceleration potential on the 26.0 kg/m3 isopycnal showed persistent poleward inshore flow for all cruises and...100 km from shore that divided low offshore and high inshore spiciness. The 26.0 kg/m3 isopycnal sloped upward toward the coast due to upwelling ...8  Figure 3.  The boundary conditions (and the direction convention of the

Linkages Between Upwelling and Shell Characteristics of Mytilus californianus: Morphology and Stable Isotope (δ13C, δ18O) Signatures of a Carbonate Archive from the California Current

NASA Astrophysics Data System (ADS)

Hosfelt, J. D.; Hill, T. M.; Russell, A. D.; Bean, J. R.; Sanford, E.; Gaylord, B.

2014-12-01

Many calcareous organisms are known to record the ambient environmental conditions in which they grow, and their calcium carbonate skeletons are often valuable archives of climate records. Mytilus californianus, a widely distributed species of intertidal mussel, experiences a spatial mosaic of oceanographic conditions as it grows within the California Current System. Periodic episodes of upwelling bring high-CO2 waters to the surface, during which California coastal waters are similar to projected conditions and act as a natural analogue to future ocean acidification. To examine the link between upwelling and shell characteristics of M. californianus, we analyzed the morphology and stable isotope (δ13C, δ18O) signatures of mussel specimens collected live from seven study sites within the California Current System. Morphometric analyses utilized a combination of elliptic Fourier analysis and shell thickness measurements to determine the influence of low pH waters on the growth morphology and ecological fitness of M. californianus. These geochemical and morphological analyses were compared with concurrent high-resolution environmental (T, S, pH, TA, DIC) records from these seven study sites from 2010-2013. With appropriate calibration, new archives from modern M. californianus shells could provide a valuable tool to enable environmental reconstructions within the California Current System. These archives could in turn be used to predict the future consequences of continuing ocean acidification, as well as reconstruct past (archeological) conditions.

Upwelling Response to Hurricane Isaac in Geostrophic Oceanic Vortices

NASA Astrophysics Data System (ADS)

Jaimes, B.; Shay, L. K.; Brewster, J. K.; Schuster, R.

2013-05-01

As a tropical cyclone (TC) moves over the ocean, the cyclonic curl of the wind stress produces a region of upwelling waters under the TC center that is compensated by downwelling waters at regions outside the center. Direct measurements conducted during hurricane Rita and recent numerical studies indicate that this is not necessarily the case when TCs move over geostrophic oceanic features, where its background relative vorticity impacts wind-driven horizontal current divergence and the upwelling velocity. Modulation of the upwelling response in these energetic oceanic regimes impacts vertical mixing across the oceanic mixed layer base, air-sea fluxes into the atmosphere, and ultimately storm intensity. As part of NOAA Intensity Forecasting Experiment, an experiment was conducted during the passage of TC Isaac over the energetic geostrophic eddy field in the Gulf of Mexico in August 2012. Expendable bathythermographs, current profilers, and conductivity-temperature-depth probes were deployed in Isaac from NOAA WP-3D aircraft during four in-storm flights to measure oceanic variability and its impact on TC-driven upwelling and surface fluxes of heat and momentum. During intensification to hurricane, the cyclonic curl of the wind stress of Isaac extended over a region of more than 300 km in diameter (4 to 5 times the radius of maximum winds). Isaac's center moved over a cold cyclonic feature, while its right and left sides moved over warm anticyclones. Contrasting upwelling and downwelling regimes developed inside the region of cyclonic curl of the wind stress. Both positive (upwelling) and negative (downwelling) vertical displacements of 40 and 60 m, respectively, were measured inside the region of cyclonic curl of the wind stress, which are between 3 to 4 times larger than predicted vertical displacements for a quiescent ocean based on scaling arguments. Oceanic mixed layer (OML) currents of 0.2 to 0.7 m s-1 were measured, which are about 50% smaller than the expected velocity response under quiescent oceanic conditions. Although OML currents were measured inside the core of cyclonic curl of the wind stress, their orientation is not consistent with horizontally divergent flows typically found in upwelling regimes under TC centers. Theoretical predictions that consider background relative vorticity effects on the upwelling response mimic the contrasting upwelling/downwelling regimes inside the region of cyclonic curl of the wind stress. These results point to an important modulation of the OML current and upwelling response by background oceanic flows, where the upwelling velocity is a function of the curl of wind-intensified pre-storm geostrophic currents, rather than just a function of the curl of the wind stress. Thus, properly initializing temperature and salinity fields in numerical models is needed to accurately represent these oceanic processes in coupled forecast models.

Spiraling pathways of global deep waters to the surface of the Southern Ocean.

PubMed

Tamsitt, Veronica; Drake, Henri F; Morrison, Adele K; Talley, Lynne D; Dufour, Carolina O; Gray, Alison R; Griffies, Stephen M; Mazloff, Matthew R; Sarmiento, Jorge L; Wang, Jinbo; Weijer, Wilbert

2017-08-02

Upwelling of global deep waters to the sea surface in the Southern Ocean closes the global overturning circulation and is fundamentally important for oceanic uptake of carbon and heat, nutrient resupply for sustaining oceanic biological production, and the melt rate of ice shelves. However, the exact pathways and role of topography in Southern Ocean upwelling remain largely unknown. Here we show detailed upwelling pathways in three dimensions, using hydrographic observations and particle tracking in high-resolution models. The analysis reveals that the northern-sourced deep waters enter the Antarctic Circumpolar Current via southward flow along the boundaries of the three ocean basins, before spiraling southeastward and upward through the Antarctic Circumpolar Current. Upwelling is greatly enhanced at five major topographic features, associated with vigorous mesoscale eddy activity. Deep water reaches the upper ocean predominantly south of the Antarctic Circumpolar Current, with a spatially nonuniform distribution. The timescale for half of the deep water to upwell from 30° S to the mixed layer is ~60-90 years.Deep waters of the Atlantic, Pacific and Indian Oceans upwell in the Southern Oceanbut the exact pathways are not fully characterized. Here the authors present a three dimensional view showing a spiralling southward path, with enhanced upwelling by eddy-transport at topographic hotspots.

The circulation dynamics associated with a northern Benguela upwelling filament during October 2010

NASA Astrophysics Data System (ADS)

Muller, Annethea A.; Mohrholz, Volker; Schmidt, Martin

2013-07-01

Upwelling filaments, a common feature in all the major upwelling systems, are also regularly observed in the Benguela upwelling system and are thought to provide an effective mechanism for the exchange of matter between the shelf and the open ocean. The mesoscale dynamics of a northern Benguela upwelling filament located at approximately 18.5°S were examined and the associated transport was quantified. The development of the filament was tracked using optimal interpolated SST satellite data and two transects were consequently sampled across the feature using a towed undulating CTD (ScanFish). Additional hydrographic, nutrient and biological parameters were investigated at several stations along each transect. Following 7 days of strong upwelling favorable winds, sampling coincided with a period of relative wind relaxation and the filament was presumably in a decaying state. The basic mesoscale structure of the investigated filament corresponded well to what had previously been described for filaments from other eastern boundary current systems. The cross-shore transport associated with the filament was found to be significantly greater than the integrated Ekman transport in the region. With the combination of the high resolution dataset and a MOM-4 ecosystem model the complex mesoscale flow field associated with the feature could be observed and the counterbalancing onshore transport, associated with subsurface dipole eddies, was revealed within the filament. The results further suggest that an interaction between the offshore bending of flow at the Angola-Benguela Front (ABF), the detachment of the strong poleward flow from the coast as the thermal front meanders and the observed dipole eddies may be driving filament occurrence in the region off Cape Frio.

Does mesoscale matters in decadal changes observed in the northern Canary upwelling system?

NASA Astrophysics Data System (ADS)

Relvas, P.; Luís, J.; Santos, A. M. P.

2009-04-01

The Western Iberia constitutes the northern limb of the Canary Current Upwelling System, one of the four Eastern Boundary Upwelling Systems of the world ocean. The strong dynamic link between the atmosphere and the ocean makes these systems highly sensitive to global change, ideal to monitor and investigate its effects. In order to investigate decadal changes of the mesoscale patterns in the Northern Canary upwelling system (off Western Iberia), the field of the satellite-derived sea surface temperature (SST) trends was built at the pixel scale (4x4 km) for the period 1985-2007, based on the monthly mean data from the Advanced Very High Resolution Radiometer (AVHRR) on board NOAA series satellites, provided by the NASA Physical Oceanography Distributed Active Archive Center (PO.DAAC) at the Jet Propulsion Laboratory. The time series were limited to the nighttime passes to avoid the solar heating effect and a suite of procedures were followed to guarantee that the temperature trends were not biased towards the seasonally more abundant summer data, when the sky is considerably clear. A robust linear fit was applied to each individual pixel, crossing along the time the same pixel in all the processed monthly mean AVHRR SST images from 1985 until 2007. The field of the SST trends was created upon the slopes of the linear fits applied to each pixel. Monthly mean SST time series from the one degree enhanced International Comprehensive Ocean-Atmosphere Data Set (ICOADS) and from near-shore measurements collected on a daily basis by the Portuguese Meteorological Office (IM) are also used to compare the results and extend the analysis back until 1960. A generalized warming trend is detected in the coastal waters off Western Iberia during the last decades, no matter which data set we analyse. However, significant spatial differences in the warming rates are observed in the satellite-derived SST trends. Remarkably, off the southern part of the Western Iberia the known upwelling pattern is clearly reflected in the warming field. There, the coastal upwelled waters show a weak warming trend when compared with the offshore waters. If we assume that the SST contrast between coastal and offshore waters is a proxy for the upwelling intensity, then this fact suggests the enhancement of the upwelling regime off SW Iberia since 1985. Although the seasonal nature of the upwelling in the region, the strengthening must be significant since it leaves a coherent imprint in the annual warming field. An analysis done on a monthly basis reveals that the central months of the classical upwelling season (July to September) are the responsible for this coherent mesoscale structure observed in the warming field off SW Iberia. The same conclusions are not clear for the mesoscale structure further north, where no significant differences are observed between the coastal and offshore warming rates. To investigate if our results, obtained for the period with satellite coverage (1985-2007), could be extended or not until 1960, we computed an upwelling index as the SST difference between coastal and offshore ICOADS SST. The analysis revealed that the trends are different whether we consider the whole time series or only the period investigated with the satellite imagery. We can suppose a relatively unchanged upwelling regime if we consider the period 1960-2005, but a rapid increase of intensity if we consider the period from 1985 onwards, particularly in the most southern regions, in agreement with the satellite imagery analysis. Our present results point out that mesoscale activity can account for larger changes in local SST than global average trends. In Eastern Boundary Upwelling Systems, where mesoscale structures play a major role in the description of the upwelling regime, to rely on sparse spatial observations to hypothesize about the decadal behaviour of the upwelling intensity at the basin scale may be questionable.

Oceanographic, Air-sea Interaction, and Environmental Aspects of Artificial Upwelling Produced by Wave-Inertia Pumps for Potential Hurricane Intensity Mitigation

NASA Astrophysics Data System (ADS)

Soloviev, A.; Dean, C.

2017-12-01

The artificial upwelling system consisting of the wave-inertia pumps driven by surface waves can produce flow of cold deep water to the surface. One of the recently proposed potential applications of the artificial upwelling system is the hurricane intensity mitigation. Even relatively small reduction of intensity may provide significant benefits. The ocean heat content (OHC) is the "fuel" for hurricanes. The OHC can be reduced by mixing of the surface layer with the cold water produced by wave-inertia pumps. Implementation of this system for hurricane mitigation has several oceanographic and air-sea interaction aspects. The cold water brought to the surface from a deeper layer has higher density than the surface water and, therefore, tends to sink back down. The mixing of the cold water produced by artificial upwelling depends on environmental conditions such as stratification, regional ocean circulation, and vertical shear. Another aspect is that as the sea surface temperature drops below the air temperature, the stable stratification develops in the atmospheric boundary layer. The stable atmospheric stratification suppresses sensible and latent heat air-sea fluxes and reduces the net longwave irradiance from the sea surface. As a result, the artificial upwelling may start increasing the OHC (though still reducing the sea surface temperature). In this work, the fate of the cold water in the stratified environment with vertical shear has been studied using computational fluid dynamics (CFD) tools. A 3D large eddy simulation model is initialized with observational temperature, salinity, and current velocity data from a sample location in the Straits of Florida. A periodic boundary condition is set along the direction of the current, which allows us to simulate infinite fetch. The model results indicate that the cold water brought to the sea surface by a wave-inertia pump forms a convective jet. This jet plunges into the upper ocean mixed layer and penetrates the thermocline. On the way down, the jet partially mixes with the surrounding water reducing the temperature of the upper ocean. The OHC thus can either reduce or increase, depending on the wave-inertia pump parameters. Based on the model results, we discuss feasibility of the implementation of the artificial upwelling system for hurricane intensity mitigation.

Implications of Upwells as Hydrodynamic Jets in a Pulse Jet Mixed System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pease, Leonard F.; Bamberger, Judith A.; Minette, Michael J.

This report evaluates the physics of the upwell flow in pulse jet mixed systems in the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Although the initial downward flow and radial flow from jets characteristic of pulse jet mixers (PJMs) has been analyzed, the upwells have received considerably less attention despite having significant implications for vessel mixing. Do the upwells behave like jets? How do the upwells scale? When will the central upwell break through? What proportion of the vessel is blended by the upwells themselves? Indeed, how the physics of the central upwell is affected by multiple PJMs (e.g.,more » six in the proposed mixing vessels), non-Newtonian rheology, and significant multicomponent solids loadings remain unexplored.« less

Impact of Equatorial Waves on the Variability of Upwelling Process Along West Coast of India

NASA Astrophysics Data System (ADS)

Prakash, K. R.; Nigam, T.; Pant, V.

2017-12-01

Coastal upwelling is a seasonal phenomenon along the south eastern Arabian Sea (SEAS) due to favourable wind setup during Indian Summer Monsoon Season (June-September). This upwelling brings subsurface cold and nutrient rich water to the surface layers. The cold water transported northward by the altered along shore current of west coast of India in the post-monsoon season. The different climatological forcing of positive Indian Ocean Dipole (IOD) and normal years were utilised to simulate the upwelling off the west coast of India using a three dimensional Regional Ocean Modelling System (ROMS). Strength of upwelling and the northward transport were found to be weaken for positive IOD simulations as compared to normal years. Analysis suggests that the meridional wind stress weakening resulted into a decrease in strength of West India Coastal Current (WICC) and, therefore, reduced magnitude of offshore Ekman transport. The mixed layer heat budget calculation also supports the findings by showing dominated vertical process in comparison to net heat flux effect. The post-monsoon northward transport of cold water was found to be correlated with the coastally trapped downwelling Kelvin waves. These waves are the only remote forcing from the Bay of Bengal that reaches to the south-eastern Arabian Sea during the months of October-December. The composite of sea surface height anomalies for the positive IOD and normal years shows that the downwelling Kelwin wave was absent during October-December.

Counterintuitive effects of global warming-induced wind patterns on primary production in the Northern Humboldt Current System.

PubMed

Mogollón, Rodrigo; R Calil, Paulo H

2018-07-01

It has been hypothesized that global warming will strengthen upwelling-favorable winds in the Northern Humboldt Current System (NHCS) as a consequence of the increase of the land-sea thermal gradient along the Peruvian coast. The effect of strengthened winds in this region is assessed with the use of a coupled physical-biogeochemical model forced with projected and climatological winds. Strengthened winds induce an increase in primary production of 2% per latitudinal degree from 9.5°S to 5°S. In some important coastal upwelling sites primary production is reduced. This is due to a complex balance between nutrient availability, nutrient use efficiency, as well as eddy- and wind-driven factors. Mesoscale activity induces a net offshore transport of inorganic nutrients, thus reducing primary production in the coastal upwelling region. Wind mixing, in general disadvantageous for primary producers, leads to shorter residence times in the southern and central coastal zones. Overall, instead of a proportional enhancement in primary production due to increased winds, the NHCS becomes only 5% more productive (+5 mol C m -2 year -1 ), 10% less limited by nutrients and 15% less efficient due to eddy-driven effects. It is found that regions with a initial strong nutrient limitation are more efficient in terms of nutrient assimilation which makes them more resilient in face of the acceleration of the upwelling circulation. © 2018 John Wiley & Sons Ltd.

Iberian and California-Oregon Upwelling Systems: trends and status of two upwelling systems at the same latitude over the last four decades.

NASA Astrophysics Data System (ADS)

Barreiro, B.; Barton, E. D.

2012-04-01

The study of Eastern Boundary Upwelling Systems is of vital importance, given the interest in rational management of the fisheries resources. The high level of biogeochemical activity associated with the physical process of upwelling increases primary production and enriches the living resources of these areas. This presentation focuses on the variability of these physical processes on daily to interdecadal scales, in an investigation of the effects of climate change in the Iberian and California-Oregon Upwelling Systems. The Upwelling Index (UI) was analysed for the period 1967-2010 at 35.5-44.5°N in both areas. The two systems differ in that the magnitudes of upwelling intensity off California-Oregon are 3.3 higher than off Iberia but they show a similar latitudinal behaviour. The annual/interannual scale variability of upwelling can be represented by the recently introduced Cumulative Upwelling Index (CUI) based on summing the mean daily UI. The seasonal cycle results show the length of upwelling season increases southwards from 180 to 300 days and a net upwelling occurs only for latitudes lower than 43°N. On the interannual scales, the CUI showed a roughly linear change at high and low latitudes (R>0.9), with slopes between 250 and -130 m3 s-1 km-1 day-1 in Iberian and 620 and -290 m3 s-1 km-1 day-1 in California-Oregon. The central areas (40.5-42.5°N) are less stable and shifted between net upwelling and downwelling over extended periods. This information helps us contextualize the present state of the study area and interpreted ongoing intensive process-oriented studies within the longer term variability.

Bleaching susceptibility and recovery of Colombian Caribbean corals in response to water current exposure and seasonal upwelling.

PubMed

Bayraktarov, Elisa; Pizarro, Valeria; Eidens, Corvin; Wilke, Thomas; Wild, Christian

2013-01-01

Coral bleaching events are globally occurring more frequently and with higher intensity, mainly caused by increases in seawater temperature. In Tayrona National Natural Park (TNNP) in the Colombian Caribbean, local coral communities are subjected to seasonal wind-triggered upwelling events coinciding with stronger water currents depending on location. This natural phenomenon offers the unique opportunity to study potential water current-induced mitigation mechanisms of coral bleaching in an upwelling influenced region. Therefore, coral bleaching susceptibility and recovery patterns were compared during a moderate and a mild bleaching event in December 2010 and 2011, and at the end of the subsequent upwelling periods at a water current-exposed and -sheltered site of an exemplary bay using permanent transect and labeling tools. This was accompanied by parallel monitoring of key environmental variables. Findings revealed that in 2010 overall coral bleaching before upwelling was significantly higher at the sheltered (34%) compared to the exposed site (8%). Whereas 97% of all previously bleached corals at the water current-exposed site had recovered from bleaching by April 2011, only 77% recovered at the sheltered site, but 12% had died there. In December 2011, only mild bleaching (<10% at both sites) was observed, but corals recovered significantly at both sites in the course of upwelling. No differences in water temperatures between sites occurred, but water current exposure and turbidity were significantly higher at the exposed site, suggesting that these variables may be responsible for the observed site-specific mitigation of coral bleaching. This indicates the existence of local resilience patterns against coral bleaching in Caribbean reefs.

Bleaching Susceptibility and Recovery of Colombian Caribbean Corals in Response to Water Current Exposure and Seasonal Upwelling

PubMed Central

Bayraktarov, Elisa; Pizarro, Valeria; Eidens, Corvin; Wilke, Thomas; Wild, Christian

2013-01-01

Coral bleaching events are globally occurring more frequently and with higher intensity, mainly caused by increases in seawater temperature. In Tayrona National Natural Park (TNNP) in the Colombian Caribbean, local coral communities are subjected to seasonal wind-triggered upwelling events coinciding with stronger water currents depending on location. This natural phenomenon offers the unique opportunity to study potential water current-induced mitigation mechanisms of coral bleaching in an upwelling influenced region. Therefore, coral bleaching susceptibility and recovery patterns were compared during a moderate and a mild bleaching event in December 2010 and 2011, and at the end of the subsequent upwelling periods at a water current-exposed and -sheltered site of an exemplary bay using permanent transect and labeling tools. This was accompanied by parallel monitoring of key environmental variables. Findings revealed that in 2010 overall coral bleaching before upwelling was significantly higher at the sheltered (34%) compared to the exposed site (8%). Whereas 97% of all previously bleached corals at the water current-exposed site had recovered from bleaching by April 2011, only 77% recovered at the sheltered site, but 12% had died there. In December 2011, only mild bleaching (<10% at both sites) was observed, but corals recovered significantly at both sites in the course of upwelling. No differences in water temperatures between sites occurred, but water current exposure and turbidity were significantly higher at the exposed site, suggesting that these variables may be responsible for the observed site-specific mitigation of coral bleaching. This indicates the existence of local resilience patterns against coral bleaching in Caribbean reefs. PMID:24282551

Boundary current instabilities, upwelling, shelf mixing and eutrophication processes in the Black Sea

NASA Astrophysics Data System (ADS)

Sur, Hali˙l. İ.; Özsoy, Emi˙n.; Ünlüata, Ümi˙t.

Satellite and in situ data are utilized to investigate the mesoscale dynamics of the Black Sea boundary current system with special emphasis on aspects of transport and productivity. The satellite data are especially helpful in capturing rapid sub-mesoscale motions insufficiently resolved by the in situ measurements. Various forms of isolated features, including dipole eddies and river plumes, are identified in the satellite images. Unstable flow structures at these sites appear to transport materials and momentum across the continental shelf. Species differentiation and competition are evident along the boundary current system and at the frontal regions during the development of early summer productivity. A time series of Coastal Zone Colour Scanner (CZCS) images indicate dynamical modulation of the springtime surface productivity in the southern Black Sea. Unstable meandering motions generated at Sakarya Canyon propagate east with speeds of ∼10-15 km d -1. Within weeks, a turbulent jet is created which separates from the coast, covering the entire southwestern sector. The nutrients driving the phytoplankton production (mainly Emiliana huxleyi) of the current system evidently originate from fluvial discharge entering from the northwestern region including the Danube river. The productivity pattern develops in early summer when the Danube inflow is at its peak, and through meandering motions spreads into an area several times wider than the continental shelf. In 1980, the CZCS data, and in 1991 and 1992, the Advanced Very High Resolution Radiometer (AVHRR) data indicate patches of upwelling along the west Anatolian coastline between Sakarya Canyon and Cape İnce ( Ince Burun) in summer. The upwelling phenomenon is outstanding because it occurs on a coast where normally the surface convergence near the coast implies downwelling, and under conditions of unfavorable winds. In 1992, the hydrographic data indicated the upwelling to be the result of a surface divergence of the boundary current, and sequences of satellite data indicate the role of transient dynamics. The in situ data showed the upwelling centres to be devoid of phytoplankton as well as fish eggs and larvae. The AVHRR and in situ hydrographic data in winter 1990 indicate cold water is formed over the entire western Black Sea continental shelf. The band of cold water decreases in width as it moves south and impinges on the headland at Baba Burnu, where it undergoes a sudden expansion. The maximum winter phytoplankton bloom sampled during the same period indicates explosive populations of diatoms following the band of cold water.

(abstract) Seasonal Variability in Coastal Upwelling: A Comparison of Four Coastal Upwelling Sites from Space

NASA Technical Reports Server (NTRS)

Carr, Mary-Elena

1996-01-01

Coastal upwelling of subsurface nutrient-rich water occurs along the eastern boundary of the ocean basins and leads to high primary production and fish catches. In this study satellite observations are used to compare the seasonal cycle in wind forcing and in the oceanic and biological response of the major coastal upwelling regions associated with the Canary, Benguela, California, and Humboldt Currents.

A Holocene record of ocean productivity and upwelling from the northern California continental slope

USGS Publications Warehouse

Addison, Jason A.; Barron, John A.; Finney, Bruce P.; Kusler, Jennifer E.; Bukry, David; Heusser, Linda E.; Alexander, Clark R.

2018-01-01

The Holocene upwelling history of the northern California continental slope is examined using the high-resolution record of TN062-O550 (40.9°N, 124.6°W, 550 m water depth). This 7-m-long marine sediment core spans the last ∼7500 years, and we use it to test the hypothesis that marine productivity in the California Current System (CCS) driven by coastal upwelling has co-varied with Holocene millennial-scale warm intervals. A combination of biogenic sediment concentrations (opal, total organic C, and total N), stable isotopes (organic matter δ13C and bulk sedimentary δ15N), and key microfossil indicators of upwelling were used to test this hypothesis. The record of biogenic accumulation in TN062-O550 shows considerable Holocene variability despite being located within 50 km of the mouth of the Eel River, which is one of the largest sources of terrigenous sediment to the Northeast Pacific Ocean margin. A key time interval beginning at ∼2900 calibrated years before present (cal yr BP) indicates the onset of modern upwelling in the CCS, and this period also corresponds to the most intense period of upwelling in the last 7500 years. When these results are placed into a regional CCS context during the Holocene, it was found that the timing of upwelling intensification at TN062-O550 corresponds closely to that seen at nearby ODP Site 1019, as well as in the Santa Barbara Basin of southern California. Other CCS records with less refined age control show similar results, which suggest late Holocene upwelling intensification may be synchronous throughout the CCS. Based on the strong correspondence between the alkenone sea surface temperature record at ODP Site 1019 and the onset of late Holocene upwelling in northern California, we suggest that CCS warming may be conducive to upwelling intensification, though future changes are unclear as the mechanisms forcing SST variability may differ.

A Holocene record of ocean productivity and upwelling from the northern California continental slope

NASA Astrophysics Data System (ADS)

Addison, J. A.; Barron, J. A.; Finney, B.; Kusler, J. E.; Bukry, D.; Heusser, L. E.; Alexander, C. R., Jr.

2016-12-01

The Holocene upwelling history of the northern California continental slope is examined using a 7-m-long marine sediment core (TN062-O550; 40.9°N, 124.6°W, 550 m water depth) collected offshore from Eureka, CA, that spans the last 7,400 calibrated years before present (cal yrs BP). A combination of biogenic sediment concentrations (opal, total organic C, and total N), stable isotopes (organic matter δ13C and bulk sedimentary δ15N), and key microfossil indicators of upwelling were used to test the hypothesis that marine productivity in the California Current System (CCS) driven by coastal upwelling has co-varied with global Holocene millennial-scale warm intervals. Results show biogenic sediment accumulation in TN062-O550 varied considerably during the Holocene, despite being located within 50 km of the mouth of the Eel River, one of the largest sources of terrigenous sediment to the Northeast Pacific Ocean margin. A key time interval beginning at 2900 cal yr BP indicates the onset of modern upwelling in the CCS, and that this period also corresponds to the most intense period of upwelling in the last 7,400 years. When these results are placed into a regional CCS context during the Holocene, it was found that the timing of upwelling intensification as recorded in TN062-O550 corresponds closely to that seen at nearby ODP Site 1019 as well as in the Santa Barbara Basin of southern California. Other CCS records with less high-quality age control show similar results, which suggest late Holocene upwelling intensification may be synchronous throughout the CCS. Based on the strong correspondence between the alkenone-derived sea surface temperature record at ODP Site 1019 and the onset of late Holocene upwelling in northern California, we tentatively suggest that regional CCS warming may be conducive to upwelling intensification in the future.

Coastal upwelling and downwelling forcing of circulation in a semi-enclosed bay: Ria de Vigo

NASA Astrophysics Data System (ADS)

Barton, E. D.; Largier, J. L.; Torres, R.; Sheridan, M.; Trasviña, A.; Souza, A.; Pazos, Y.; Valle-Levinson, A.

2015-05-01

Semi-enclosed bays in upwelling regions are exposed to forcing related to winds, currents and buoyancy over the shelf. The influence of this external forcing is moderated by factors such as connectivity to the open ocean, shelter by surrounding topography, dimensions of the bay, and freshwater outflows. Such bays, preferred locations for ports, mariculture, marine industry, recreational activities and coastal settlement, present a range of characteristics, understanding of which is necessary to their rational management. Observations in such a semi-enclosed bay, the Ria de Vigo in Spain, are used to characterize the influence of upwelling and downwelling pulses on its circulation. In this location, near the northern limit of the Iberian upwelling system, upwelling events dominate during a short summer season and downwelling events the rest of the year. The ria response to the external forcing is central to nutrient supply and resultant plankton productivity that supports its high level of cultured mussel production. Intensive field studies in September 2006 and June 2007 captured a downwelling event and an upwelling event, respectively. Data from eight current profiler moorings and boat-based MiniBat/ADCP surveys provided an unprecedented quasi-synoptic view of the distribution of water masses and circulation patterns in any ria. In the outer ria, circulation was dominated by the introduction of wind-driven alongshore flow from the external continental shelf through the ria entrances and its interaction with the topography. In the middle ria, circulation was primarily related to the upwelling/downwelling cycle, with a cool, salty and dense lower layer penetrating to the inner ria during upwelling over the shelf. A warmer, lower salinity and less dense surface layer of coastal waters flowed inward during downwelling. Without external forcing, the inner ria responded primarily to tides and buoyancy changes related to land runoff. Under both upwelling and downwelling conditions, the flushing of the ria involved shelf responses to wind pulses. Their persistence for a few days was sufficient to allow waters from the continental shelf to penetrate the innermost ria. Longer term observations supported by numerical modeling are required to confirm the generality of such flushing events in the ria and determine their typical frequency, while comparative studies should explore how these scenarios fit into the range of conditions experienced in other semi-enclosed bays.

Holocene variability in the intensity of wind-gap upwelling in the tropical eastern Pacific

USGS Publications Warehouse

Toth, Lauren T.; Aronson, Richard B.; Cheng, Hai; Edwards, R. Lawrence

2015-01-01

Wind-driven upwelling in Pacific Panamá is a significant source of oceanographic variability in the tropical eastern Pacific. This upwelling system provides a critical teleconnection between the Atlantic and tropical Pacific that may impact climate variability on a global scale. Despite its importance to oceanographic circulation, ecology, and climate, little is known about the long-term stability of the Panamanian upwelling system or its interaction with climatic forcing on millennial time scales. Using a combination of radiocarbon and U-series dating of fossil corals collected in cores from five sites across Pacific Panamá, we reconstructed the local radiocarbon reservoir correction, ΔR, from ~6750 cal B.P. to present. Because the ΔR of shallow-water environments is elevated by upwelling, our data set represents a millennial-scale record of spatial and temporal variability of the Panamanian upwelling system. The general oceanographic gradient from relatively strong upwelling in the Gulf of Panamá to weak-to-absent upwelling in the Gulf of Chiriquí was present throughout our record; however, the intensity of upwelling in the Gulf of Panamá varied significantly through time. Our reconstructions suggest that upwelling in the Gulf of Panamá is weak at present; however, the middle Holocene was characterized by periods of enhanced upwelling, with the most intense upwelling occurring just after of a regional shutdown in the development of reefs at ~4100 cal B.P. Comparisons with regional climate proxies suggest that, whereas the Intertropical Convergence Zone is the primary control on modern upwelling in Pacific Panamá, the El Niño–Southern Oscillation drove the millennial-scale variability of upwelling during the Holocene.

Oceanographic implications of the Cabo Catoche (Northeast Yucatan) upwelling and its effects on the coastal ecosystem

NASA Astrophysics Data System (ADS)

Reyes-Mendoza, O.; Marino-Tapia, I.; Herrera Silveira, J.; Cárdenas-Palómo, N.; Ruiz, G.

2013-05-01

The coasts of the world where upwelling events occur are intrinsically related to the human population, mainly because of their large fisheries, socioeconomic repercussion and implications concerning the health of the ecosystem. In the northeast of the Yucatan Peninsula occurs an upwelling event known as the Yucatan upwelling (YU) associated with the current of the same name. The mechanisms that generate the YU are still under discussion. In terms of seasonality it is agreed that this is annual, occurring between April and September. During spring and summer, the northeast coast of the Peninsula between CaboCatoche and Isla Contoy becomes a productive and diverse pelagic ecosystem, unique to the region. It is classified as a priority marine zone host to close to 59 species protected by the national laws. It is also recognized as an important priority marine site because of its fishery. Also, the largest global aggregation of whale sharks, the world's biggest fish, is found at this site. There is a strong connection between the physical and the biological components of the system, however the coastal extent, seasonality, and magnitude of these processes need to be determined. Therefore an in-situ study was designed in the coastal region of CaboCatoche, where a 50 km transect was positioned along shelf and another across shelf 20 km, where water was collected to determine nutrient concentrations and CTD profiles were casted during the summer of 2007, 2008 and 2011. Two acoustic profilers were installed 12 km from the coast, which recorded currents and temperature by 2 years. Another profiler located 17 km from the coast to recorded data by 8 years. Atmospheric pressure and temperature were measured, as a wind fields from NOAA. Maps were created for the vertical distribution of temperature (18-31°C), salinity (35-38 psu), density (22-27 kg/m3) and chlorophyll (0.05-12.7 mg/m3). Frequency periods were estimated for temperature, currents, wind and atmospheric pressure using spectral analysis and wavelets. In order to establish associations between the physical, chemical and biological variables multivariate analyses were performed. Based in temperature the results indicate that the upwelling occurs in pulses of two different time periods; 2-4 days and the other 8 to16 days, from March to September, associated with a decrease in sea level (-0.008±0.03 m) and variation in the V component of the current (0.007±0.006 m/s to the north). On the year the dominant tides are diurnal K1, O1 and semidiurnal M2, S2, and the U and V current component had the same periodicity during upwelling, but with not upwelling V hasn't it. The atmospheric temperature decreases the water column temperature near 10 degree during not upwelling, as also in upwelling but by other mechanisms. It is yet not possible to determine the mechanism responsible for this periodicity, however it is believed to be due to a combination of wind and Yucatan current variability. The Primary production has a response time of 2 to 3 days following the onset of the pulse and the Cla-a have an increase ten times more than the mean value.

Steps in the intensification of Benguela upwelling over the Walvis Ridge during Miocene and Pliocene

NASA Astrophysics Data System (ADS)

Hoetzel, Sebastian; Dupont, Lydie M.; Marret, Fabienne; Jung, Gerlinde; Wefer, Gerold

2017-01-01

Upwelling is a significant part of the ocean circulation controlling largely the transport of nutrient-rich cold waters to the surface and therefore influencing ocean productivity and global climate. The Benguela upwelling system (BUS) is one of the major upwelling areas in the world. Previous reconstructions of the BUS mainly focused on the onset and intensification in southern and central parts, but changes of the northern part have been rarely investigated in detail. Using the Late Miocene to Pliocene organic-walled dinoflagellate cyst record of ODP Site 1081, we reconstruct and discuss the early upwelling history over the Walvis Ridge with a special focus on the movement of the Angola-Benguela Front (ABF). We suggest that during the Late Miocene the Angola Current flowed southwards over the Walvis Ridge more frequently than today because the ABF was probably located further south as a result of a weaker meridional temperature gradient. A possible strengthening of the meridional gradient during the latest Miocene to early Pliocene in combination with uplift of south-western Africa intensified the upwelling along the coast and increased the upwelling's filaments over the Walvis Ridge. An intermediate period from 6.2 to 5.5 Ma is shown by the dominance of Habibacysta tectata, cysts of a cool-tolerant dinoflagellate known from the northern Atlantic, indicating changing oceanic conditions contemporaneous with the Messinian Salinity Crisis. From 4.3 Ma on, the upwelling signal got stronger again and waters were well-mixed and nutrient-rich. Our results indicate a northward migration of the ABF as early as 7 Ma and the initial stepwise intensification of the BUS.

COCMP Surface Current Mapping Reveals Eddy and Upwelling Jet off Cape Mendocino

NASA Astrophysics Data System (ADS)

Crawford, G. B.; Halle, C.; Largier, J.; Stone, S.

2008-12-01

Ocean surface currents are now being measured continuously over a roughly 2000 km stretch of the western US continental shelf from south of Tijuana, Mexico to the Columbia River. A long-standing gap in this coverage was finally filled on August 12, 2008, with the installation of a long-range Seasonde radar system at Shelter Cove, California (as a part of California's COCMP project). During its first three weeks of operation, this radar has revealed a large (~170 km diameter), stable, anticyclonic eddy southwest of Cape Mendocino in this poorly studied region. Upwelling-favorable winds appear to create an upwelling jet along the eastern edge of the eddy, leading to maximum daily-averaged current speeds up to 80 cm/s, and MODIS-derived chlorophyll concentrations up to 30 mg/m3 in the jet (compared to ~1 mg/m3 in the eddy center). AVHRR data reveal SST differences between the jet and the eddy center of 1.5 to 2.5 °C during these 3 weeks. These complex circulation structures modify water pathways and may interrupt nutrient delivery to locations farther south. We discuss the spatial and temporal evolution of these features.

Phytoplankton community and environmental correlates in a coastal upwelling zone along western Taiwan Strait

NASA Astrophysics Data System (ADS)

Wang, Yu; Kang, Jian-hua; Ye, You-yin; Lin, Geng-ming; Yang, Qing-liang; Lin, Mao

2016-02-01

Upwelling system in western Taiwan Strait is important for facilitating the fishery production. This study investigated hydro-chemical properties, phytoplankton biomass, phytoplankton species composition, three-dimensional (horizontal, vertical and transect) distribution of phytoplankton abundance, as well as phytoplankton annual variation and the correlation of phytoplankton community with the upwelling of underlying current and nutrients according to samples of Fujian-Guangdong coastal upwelling zone in western Taiwan Strait from August 27 to September 8, 2009. The results manifest that the nutrient-rich cold and high salinity current on the continental shelf of South China Sea upwells to the Fujian-Guangdong coastal waters through Taiwan Bank and the surging strength to surface is weak while strong at 30-m layer. The thermohaline center of coastal upwelling shifts to the east of Dongshan Island and expanded to offshore waters in comparison with previous records. A total of 137 phytoplankton species belonging to 59 genera in 4 phyla are identified excluding the unidentified species. Diatom is the first major group and followed by dinoflagellate. Cyanobacteria mainly composed by three Trichodesmium species account for a certain proportions, while Chrysophyta are only found in offshore waters. The dominant species include Thalassionema nitzschioides, Pseudo-nitzschia pungens, Thalassionema frauenfeldii, Pseudo-nitzschia delicatissima, Rhizosolenia styliformis, Chaetoceros curvisetus, Diplopsalis lenticula and Trichodesmium thiebautii. Phytoplankton community mainly consists of eurythermal and eurytopic species, followed by warm-water species, tropic high-salinity species and oceanic eurythermic species in order. Phytoplankton abundance ranges from 1.00 × 102 ind./L ~ 437.22 × 102 ind./L with an average of 47.36 × 102 ind./L. For vertical distribution, maximum abundance is found at 30 m-depth and the surface comes second. Besides, the abundance below 30 m decreases with increasing water depth. The horizontal and transect distribution of phytoplankton abundance are both displayed in patchy size, and the peak area is the offshore waters from the east of Dongshan Island to the south of Zhangpu which is basically coincident with the thermohaline center of the upwelling, but the distribution range of phytoplankton high abundance is expanded out of the upwelling center. Phytoplankton abundances on 3 transects in offshore waters from the east of Dongshan Island to the south of Zhangpu are higher than that of nearshore waters and the other 5 transects. Moreover, the underlying current is accompanied by shade flora so as to offer a certain evidence for the presence of upwelling. Phytoplankton abundance at 30 m-depth and bottom both present low significant positive correlation with phosphate, while there are not significant correlations between the content of inorganic nitrogen and phytoplankton abundance in all water layers. The intensity and range of Fujian-guangdong coastal upwelling has a regulating effect on the species succession, abundance distribution and the location of phytoplankton peak area.

Surface circulation and upwelling patterns around Sri Lanka

NASA Astrophysics Data System (ADS)

de Vos, A.; Pattiaratchi, C. B.; Wijeratne, E. M. S.

2014-10-01

Sri Lanka occupies a unique location within the equatorial belt in the northern Indian Ocean, with the Arabian Sea on its western side and the Bay of Bengal on its eastern side, and experiences bi-annually reversing monsoon winds. Aggregations of blue whale (Balaenoptera musculus) have been observed along the southern coast of Sri Lanka during the northeast (NE) monsoon, when satellite imagery indicates lower productivity in the surface waters. This study explored elements of the dynamics of the surface circulation and coastal upwelling in the waters around Sri Lanka using satellite imagery and numerical simulations using the Regional Ocean Modelling System (ROMS). The model was run for 3 years to examine the seasonal and shorter-term (~10 days) variability. The results reproduced correctly the reversing current system, between the Equator and Sri Lanka, in response to the changing wind field: the eastward flowing Southwest Monsoon Current (SMC) during the southwest (SW) monsoon transporting 11.5 Sv (mean over 2010-2012) and the westward flowing Northeast Monsoon Current (NMC) transporting 9.6 Sv during the NE monsoon, respectively. A recirculation feature located to the east of Sri Lanka during the SW monsoon, the Sri Lanka Dome, is shown to result from the interaction between the SMC and the island of Sri Lanka. Along the eastern and western coasts, during both monsoon periods, flow is southward converging along the southern coast. During the SW monsoon, the island deflects the eastward flowing SMC southward, whilst along the eastern coast, the southward flow results from the Sri Lanka Dome recirculation. The major upwelling region, during both monsoon periods, is located along the southern coast, resulting from southward flow converging along the southern coast and subsequent divergence associated with the offshore transport of water. Higher surface chlorophyll concentrations were observed during the SW monsoon. The location of the flow convergence and hence the upwelling centre was dependent on the relative strengths of wind-driven flow along the eastern and western coasts: during the SW (NE) monsoon, the flow along the western (eastern) coast was stronger, migrating the upwelling centre to the east (west).

Scaling Coastal Ecosystems to Oceanographic and Climatic Drivers: Making Sense of Community Variation on Rocky Shores Using the Comparative-Experimental Approach in Upwelling and Downwelling Systems

NASA Astrophysics Data System (ADS)

Menge, B. A.; Gouhier, T.; Chan, F.; Hacker, S.; Menge, D.; Nielsen, K. J.

2016-02-01

Ecology focuses increasingly on the issue of matching spatial and temporal scales responsible for ecosystem pattern and dynamics. Benthic coastal communities traditionally were studied at local scales using mostly short-term research, while environmental (oceanographic, climatic) drivers were investigated at large scales (e.g., regional to oceanic, mostly offshore) using combined snapshot and monitoring (time series) research. The comparative-experimental approach combines local-scale studies at multiple sites spanning large-scale environmental gradients in combination with monitoring of inner shelf oceanographic conditions including upwelling/downwelling wind forcing and their consequences (e.g., temperature), and inputs of subsidies (larvae, phytoplankton, detritus). Temporal scale varies depending on the questions, but can extend from years to decades. We discuss two examples of rocky intertidal ecosystem dynamics, one at a regional scale (California Current System, CCS) and one at an interhemispheric scale. In the upwelling-dominated CCS, 52% and 32% of the variance in local community structure (functional group abundances at 13 sites across 725 km) was explained by external factors (ecological subsidies, oceanographic conditions, geographic location), and species interactions, respectively. The interhemispheric study tested the intermittent upwelling hypothesis (IUH), which predicts that key ecological processes will vary unimodally along a persistent downwelling to persistent upwelling gradient. Using 14-22 sites, unimodal relationships between ecological subsidies (phytoplankton, prey recruitment), prey responses (barnacle colonization, mussel growth) and species interactions (competition rate, predation rate and effect) and the Bakun upwelling index calculated at each site accounted for 50% of the variance. Hence, external factors can account for about half of locally-expressed community structure and dynamics.

Diatoms as a paleoproductivity proxy in the NW Iberian coastal upwelling system (NE Atlantic)

NASA Astrophysics Data System (ADS)

Zúñiga, Diana; Santos, Celia; Froján, María; Salgueiro, Emilia; Rufino, Marta M.; De la Granda, Francisco; Figueiras, Francisco G.; Castro, Carmen G.; Abrantes, Fátima

2017-03-01

The objective of the current work is to improve our understanding of how water column diatom's abundance and assemblage composition is seasonally transferred from the photic zone to seafloor sediments. To address this, we used a dataset derived from water column, sediment trap and surface sediment samples recovered in the NW Iberian coastal upwelling system. Diatom fluxes (2.2 (±5.6) 106 valves m-2 d-1) represented the majority of the siliceous microorganisms sinking out from the photic zone during all studied years and showed seasonal variability. Contrasting results between water column and sediment trap diatom abundances were found during downwelling periods, as shown by the unexpectedly high diatom export signals when diatom-derived primary production achieved their minimum levels. They were principally related to surface sediment remobilization and intense Minho and Douro river discharge that constitute an additional source of particulate matter to the inner continental shelf. In fact, contributions of allochthonous particles to the sinking material were confirmed by the significant increase of both benthic and freshwater diatoms in the sediment trap assemblage. In contrast, we found that most of the living diatom species blooming during highly productive upwelling periods were dissolved during sinking, and only those resistant to dissolution and the Chaetoceros and Leptocylindrus spp. resting spores were susceptible to being exported and buried. Furthermore, Chaetoceros spp. dominate during spring-early summer, when persistent northerly winds lead to the upwelling of nutrient-rich waters on the shelf, while Leptocylindrus spp. appear associated with late-summer upwelling relaxation, characterized by water column stratification and nutrient depletion. These findings evidence that the contributions of these diatom genera to the sediment's total marine diatom assemblage should allow for the reconstruction of different past upwelling regimes.

Coastal upwelling seasonality and variability of temperature and chlorophyll in a small coastal embayment

NASA Astrophysics Data System (ADS)

Walter, Ryan K.; Armenta, Kevin J.; Shearer, Brandon; Robbins, Ian; Steinbeck, John

2018-02-01

While the seasonality of wind-driven coastal upwelling in eastern boundary upwelling systems has long been established, many studies describe two distinct seasons (upwelling and non-upwelling), a generalized framework that does not capture details relevant to marine ecosystems. In this contribution, we present a more detailed description of the annual cycle and upwelling seasonality for an understudied location along the central California coast. Using both the mean monthly upwelling favorable wind stress and the monthly standard deviation, we define the following seasons (contiguous months) and a transitional period (non-contiguous months): "Winter Storms" season (Dec-Jan-Feb), "Upwelling Transition" period (Mar and Jun), "Peak Upwelling" season (Apr-May), "Upwelling Relaxation" season (Jul-Aug-Sep), and "Winter Transition" season (Oct-Nov). In order to describe the oceanic response to this upwelling wind seasonality, we take advantage of nearly a decade of full water-column measurements of temperature and chlorophyll made using an automated profiling system at the end of the California Polytechnic State University Pier in San Luis Obispo Bay, a small ( 2 km wide near study site) and shallow ( 10 m average bay depth) coastal embayment. Variability and average-year patterns are described inside the bay during the various upwelling seasons. Moreover, the role of the local coastline orientation and topography on bay dynamics is also assessed using long-term measurements collected outside of the bay. The formation of a seasonally variable upwelling shadow system and potential nearshore retention zone is discussed. The observations presented provide a framework on which to study interannual changes to the average-year seasonal cycle, assess the contribution of higher-frequency features to nearshore variability, and better predict dynamically and ecologically important events.

Reconstructing Holocene Upwelling Conditions in Monterey Bay, California

NASA Astrophysics Data System (ADS)

Owen, P. W.; Wagner, A. J.; Addison, J. A.; Schwartz, V.; Barron, J. A.; Carlin, J. A.

2017-12-01

Upwelling along the eastern margin of the North Pacific is vital to the California Current System (CCS) and is a major contributing factor to the diverse marine ecosystems along the US West Coast. Prior studies hypothesize climate change will accelerate the alongshore equatorward winds that drive coastal upwelling, with the greatest increase in upwelling occurring within the poleward portion (N of 40°N) of the CCS. However, other studies have suggested that future upwelling changes in the southern portion (S of 35°N) of the CCS are less certain. Here we present a geological perspective into past Holocene upwelling along the central California coast from the Monterey Bay National Marine Sanctuary to provide a potential analogue for future upwelling conditions and a deeper understanding of CCS dynamics. A smear slide analysis of marine sediment cores taken from [1] the Pioneer Seamount off the Central California coast, [2] offshore of Pt. Año Nuevo, and [3] near the mouth of the Salinas River shows varying percentages of biogenic and terrigenous sediments during the past 11,000 years, with a shift toward greater biogenic silica sediments occurring approximately 3,000 cal yrs BP in the offshore site. In addition, an analysis of the diatom assemblages is used as a proxy for upwelling conditions. Preliminary results suggest a greater abundance of F. doliolus, a diatom species commonly used as a proxy for increased productivity and upwelling, occurs around 3,500 cal years BP. These results are then compared to existing calibrated X-ray computed tomography (CT) bulk density, total organic carbon (TOC), and biogenic silica (opal) measurements during periods of known climatic variability such as the Holocene Climate Optimum, Medieval Warm Period and Little Ice Age. Our results can provide a new high-resolution study of the central CCS throughout the Holocene, and give us a better understanding as to how future oceanic conditions may change the marine ecosystems along California's coast.

A cool upwelling filament off Namibia, southwest Africa: preliminary measurements of physical and biological features

NASA Astrophysics Data System (ADS)

Shillington, F. A.; Peterson, W. T.; Hutchings, L.; Probyn, T. A.; Waldron, H. N.; Agenbag, J. J.

1990-11-01

Mesoscale physical and biological measurements were made in a cool upwelling filament in the Benguela Current system, off Namibia in February 1988. The filament had been visible on a satellite infra-red image 2 weeks prior to the survey, and was found to be in a decaying state. Temperature, salinity, 0-50 m integratred nitrate, ammonium, oxygen and plankton data have enabled a consistent picture of the structure to be formed, involving four different water bodies. These are (1) typical continental shelf upwelled water inside the shelf break, (2) filament water characterized by salinity of 35.2, high surface integrated nitrate, small phytoplankton cells, and large numbers of salps, (3) warm, blue oligotrophic water to the north, and (4) a warm, high salinity anticyclonic eddy to the south. It is suggested that this southern eddy may have originated from the Agulhas Current near Cape Town. Anomalously low nitrate concentrations, that could not be explained, were found in a 100 m thick layer between 100 and 200 m depth on the southern edge of the structure.

Wind-driven upwelling effects on cephalopod paralarvae: Octopus vulgaris and Loliginidae off the Galician coast (NE Atlantic)

NASA Astrophysics Data System (ADS)

Otero, Jaime; Álvarez-Salgado, X. Antón; González, Ángel F.; Souto, Carlos; Gilcoto, Miguel; Guerra, Ángel

2016-02-01

Circulation patterns of coastal upwelling areas may have central consequences for the abundance and cross-shelf transport of the larval stages of many species. Previous studies have provided evidences that larvae distribution results from a combination of subtidal circulation, species-specific behaviour and larval sources. However, most of these works were conducted on organisms characterised by small-sized and abundant early life phases. Here, we studied the influence of the hydrography and circulation of the Ría de Vigo and adjacent shelf (NW Iberian upwelling system) on the paralarval abundance of two contrasting cephalopods, the benthic common octopus (Octopus vulgaris) and the pelagic squids (Loliginidae). We sampled repeatedly a cross-shore transect during the years 2003-2005 and used zero inflated models to accommodate the scarcity and patchy distribution of cephalopod paralarvae. The probability of catching early stages of both cephalopods was higher at night. Octopus paralarvae were more abundant in the surface layer at night whereas loliginids preferred the bottom layer regardless of the sampling time. Abundance of both cephalopods increased when shelf currents flowed polewards, water temperature was high and water column stability was low. The probability of observing an excess of zero catches decreased during the year for octopus and at high current speed for loliginids. In addition, the circulation pattern conditioned the body size distribution of both paralarvae; while the average size of the captured octopuses increased (decreased) with poleward currents at daylight (nighttime), squids were smaller with poleward currents regardless of the sampling time. These results contribute to the understanding of the effects that the hydrography and subtidal circulation of a coastal upwelling have on the fate of cephalopod early life stages.

The California Current System

NASA Image and Video Library

2017-12-08

This February 8, 2016 composite image reveals the complex distribution of phytoplankton in one of Earth's eastern boundary upwelling systems — the California Current. Recent work suggests that our warming climate my be increasing the intensity of upwelling in such regions with possible repercussions for the species that comprise those ecosystems. NASA's OceanColor Web is supported by the Ocean Biology Processing Group (OBPG) at NASA's Goddard Space Flight Center. Our responsibilities include the collection, processing, calibration, validation, archive and distribution of ocean-related products from a large number of operational, satellite-based remote-sensing missions providing ocean color, sea surface temperature and sea surface salinity data to the international research community since 1996. Credit: NASA/Goddard/Suomin-NPP/VIIRS NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Local atmospheric forcing driving an unexpected California Current System response during the 2015-2016 El Niño

NASA Astrophysics Data System (ADS)

Frischknecht, Martin; Münnich, Matthias; Gruber, Nicolas

2017-01-01

The 2015-2016 El Niño contributed to large anomalies across the California Current System (CalCS), but these anomalies ceased unexpectedly in late 2015. Here we use a suite of three hindcast simulations with the Regional Oceanic Modeling System to assess the responsible mechanisms for this development. We find that the early buildup was primarily driven by the early onset of this event in the tropical Pacific, driving anomalies in the CalCS through the propagation of coastally trapped waves. In contrast, the abrupt end in the central CalCS was caused by the unusual onset of upwelling favorable winds in the fall of 2015, which offset the continuing remote forcing through the coastal waveguide. Nevertheless, low-nutrient anomalies persisted, causing anomalously low phytoplankton abundance in the upwelling season of 2016. This is a recurring pattern for all El Niño events over the last 37 years, suggesting predictive skill on seasonal timescales.

Tracking the Surface Circulation in Coastal Upwelling off Central and Northern California over Long Times and Large Areas.

NASA Astrophysics Data System (ADS)

Largier, J. L.; Garcia-Reyes, M.; Bjorkstedt, E.; Paduan, J. D.

2016-12-01

More than a decade of HF Radar data off central and northern California provides an unprecedented view of the flow structures and interannual variability in surface circulation in a coastal upwelling area. The interaction of the alongshore shelf jet with shoreline features and mesoscale eddies is well represented in direct analyses of HFR data and also important in improving the performance of data-assimilating models. While invaluable for operational response in the short-term, this long-term record of surface circulation is equally invaluable in ecosystem oceanography. With direct measurement of currents, the different expressions of upwelling can be disaggregated. Wind forcing, transport patterns and water properties can be evaluated independently and indexed independently. In doing this, it becomes clear that wind-current-temperature correlations change from place to place and year to year in any given region and that a single "upwelling index" is a blunt tool to track changes in pelagic and benthic communities in coastal upwelling areas.

Observations of a cycle of intense coastal upwelling and downwelling at the research site of the Shirshov Institute of Oceanology in the Black Sea

NASA Astrophysics Data System (ADS)

Zatsepin, A. G.; Silvestrova, K. P.; Kuklev, S. B.; Piotoukh, V. B.; Podymov, O. I.

2016-03-01

The paper presents the results of joint analysis of the response of vertical temperature and current velocity profile distributions in the coastal zone of the Gelendzhik region of the Black Sea to strong wind forcing in the third ten-day period of September 2013. This forcing was caused by the propagation of an atmospheric cyclone, which first initiated coastal upwelling that was later replaced by downwelling. We formulate a criterion for the development of full coastal upwelling and demonstrate its efficiency. We assume that frequent events of incomplete coastal upwelling and downwelling are associated with changes in the water dynamics (variations in the intensity and direction of the alongshore current) generally not related to local wind forcing.

Recent 121-year variability of western boundary upwelling in the northern South China Sea

NASA Astrophysics Data System (ADS)

Liu, Yi; Peng, Zicheng; Shen, Chuan-Chou; Zhou, Renjun; Song, Shaohua; Shi, Zhengguo; Chen, Tegu; Wei, Gangjian; Delong, Kristine L.

2013-06-01

upwelling is typically related to the eastern boundary upwelling system, whereas the powerful southwest Asian summer monsoon can also generate significant cold, nutrient-rich deep water in western coastal zones. Here we present a sea surface temperature record (A.D. 1876-1996) derived from coral Porites Sr/Ca for an upwelling zone in the northern South China Sea. The upwelling-induced sea surface temperature anomaly record reveals prominent multidecadal variability driven by Asian summer monsoon dynamics with an abrupt transition from warmer to colder conditions in 1930, and a return to warmer conditions after 1960. Previous studies suggest the expected increase in atmospheric CO2 for the coming decades may result in intensification in the eastern boundary upwelling system, which could enhance upwelling of CO2-rich deep water thus exacerbating the impact of acidification in these productive zones. In contrast, the weakening trend since 1961 in the upwelling time series from the northern South China Sea suggests moderate regional ocean acidification from upwelling thus a stress relief for marine life in this region.

Numerical Study on the influence of Kuroshio Intrusion on Coastal upwelling off Coasts of China

NASA Astrophysics Data System (ADS)

Dezhou, Y.; Yin, B.

2016-02-01

Anomalous distribution of sea surface temperature (SST) has been observed off coasts of Zhejiang province, China in summer 2009 and 2012, respectively, where algal blooms are increasingly reported. Then, the rotated empirical orthogonal functions analysis has been employed to examine the 31 summertime SST fields. A distinct SST mode is identified in this upwelling area, and its principal components show a colder phase in 2009 and a warmer phase in 2012. At the same time, cruise data show colder and more saline bottom water in this upwelling area in summer 2009 relative to that in summer 2012, which implies a more nearshore Kuroshio branch current (NKBC) in summer 2009 and a more offshore NKBC in summer 2012. On the basis of regional ocean model system (ROMS), 20-year hindcast run has been successfully carried out. Model results faithfully reproduce the anomalous SST in summer 2009 and 2012. On the basis of the observational and modeled evidences, we propose that the anomalously cold or warm coastal upwelling is mainly attributed to the extremely shoreward or seaward shift of the NKBC. In other words, the more shoreward the NKBC shift, the colder the surface upwelling water is. In contrast, the more seaward the NKBC shift, the warmer the surface upwelling water is. Moreover, this paper shows a good example that the coastal environment may be profoundly influenced by the remote variation of Kuroshio east of Taiwan, which is highly correlated to the sea surface height east of Taiwan.

Dynamics of a "low-enrichment high-retention" upwelling center over the southern Senegal shelf

NASA Astrophysics Data System (ADS)

Ndoye, Siny; Capet, Xavier; Estrade, Philippe; Sow, Bamol; Machu, Eric; Brochier, Timothée.; Döring, Julian; Brehmer, Patrice

2017-05-01

Senegal is the southern tip of the Canary upwelling system. Its coastal ocean hosts an upwelling center which shapes sea surface temperatures between latitudes 12° and 15°N. Near this latter latitude, the Cape Verde headland and a sudden change in shelf cross-shore profile are major sources of heterogeneity in the southern Senegal upwelling sector (SSUS). SSUS dynamics is investigated by means of Regional Ocean Modeling System simulations. Configuration realism and resolution (Δx≈ 2 km) are sufficient to reproduce the SSUS frontal system. Our main focus is on the 3-D upwelling circulation which turns out to be profoundly different from 2-D theory: cold water injection onto the shelf and upwelling are strongly concentrated within a few tens of kilometers south of Cape Verde and largely arise from flow divergence in the alongshore direction; a significant fraction of the upwelled waters are retained nearshore over long distances while travelling southward under the influence of northerly winds. Another source of complexity, regional-scale alongshore pressure gradients, also contributes to the overall retention of upwelled waters over the shelf. Varying the degree of realism of atmospheric and oceanic forcings does not appreciably change these conclusions. This study sheds light on the dynamics and circulation underlying the recurrent sea surface temperature pattern observed during the upwelling season and offers new perspectives on the connections between the SSUS physical environment and its ecosystems. It also casts doubt on the validity of upwelling intensity estimations based on simple Ekman upwelling indices at such local scales.

The relationship between Arabian Sea upwelling and Indian Monsoon revisited

NASA Astrophysics Data System (ADS)

Yi, Xing; Zorita, Eduardo; Hünicke, Birgit

2015-04-01

Coastal upwelling is important to marine ecosystems and human activities. It transports nutrient-rich deep water mass that supports marine biological productivity. In this study, we aim to characterize the large-scale climate forcings that drive upwelling along the western Arabian Sea coast. Studies based on ocean sediments suggest that there is a link between this coastal upwelling system and the Indian summer monsoon. However, a more direct method is needed to examine the influence of various forcings on upwelling. For this purpose, we analyse a high-resolution (about 10 km) global ocean simulation (denoted STORM), which is based on the MPI-OM model developed by the Max-Planck-Institute for Meteorology in Hamburg driven by the global meteorological reanalysis NCEP over the period 1950-2010. This very high spatial resolution allows us to identify characteristics of the coastal upwelling system. We compare the simulated upwelling velocity of STORM with two traditional upwelling indices: along-shore wind speed and sea surface temperature. The analysis reveals good consistency between these variables, with high correlations between coastal upwelling and along-shore wind speed (r=0.85) as well as coastal sea surface temperature (r=-0.77). To study the impact of the monsoon on the upwelling we analyse both temporal and spatial co-variability between upwelling velocity and the Indian summer monsoon index. The spatial analysis shows that the impact of the monsoon on the upwelling is concentrated along the coast, as expected. However, somewhat unexpectedly, the temporal correlation between the coastal upwelling and the monsoon index is rather weak (r=0.26). Also, the spatial structure of upwelling in the Arabian Sea as revealed by a Principal Component Analysis is rather rich, indicating that factors other than the Monsoon are also important drivers of upwelling. In addition, no detectable trend in our coastal upwelling is found in the simulation that would match the prediction of a strengthening of upwelling under anthropogenic radiative forcing.

Has upwelling strengthened along worldwide coasts over 1982-2010?

NASA Astrophysics Data System (ADS)

Varela, R.; Álvarez, I.; Santos, F.; Decastro, M.; Gómez-Gesteira, M.

2015-05-01

Changes in coastal upwelling strength have been widely studied since 1990 when Bakun proposed that global warming can induce the intensification of upwelling in coastal areas. Whether present wind trends support this hypothesis remains controversial, as results of previous studies seem to depend on the study area, the length of the time series, the season, and even the database used. In this study, temporal and spatial trends in the coastal upwelling regime worldwide were investigated during upwelling seasons from 1982 to 2010 using a single wind database (Climate Forecast System Reanalysis) with high spatial resolution (0.3°). Of the major upwelling systems, increasing trends were only observed in the coastal areas of Benguela, Peru, Canary, and northern California. A tendency for an increase in upwelling-favourable winds was also identified along several less studied regions, such as the western Australian and southern Caribbean coasts.

Has upwelling strengthened along worldwide coasts over 1982-2010?

PubMed Central

Varela, R.; Álvarez, I.; Santos, F.;  deCastro, M.; Gómez-Gesteira, M.

2015-01-01

Changes in coastal upwelling strength have been widely studied since 1990 when Bakun proposed that global warming can induce the intensification of upwelling in coastal areas. Whether present wind trends support this hypothesis remains controversial, as results of previous studies seem to depend on the study area, the length of the time series, the season, and even the database used. In this study, temporal and spatial trends in the coastal upwelling regime worldwide were investigated during upwelling seasons from 1982 to 2010 using a single wind database (Climate Forecast System Reanalysis) with high spatial resolution (0.3°). Of the major upwelling systems, increasing trends were only observed in the coastal areas of Benguela, Peru, Canary, and northern California. A tendency for an increase in upwelling-favourable winds was also identified along several less studied regions, such as the western Australian and southern Caribbean coasts. PMID:25952477

Pathways of upwelling deep waters to the surface of the Southern Ocean

NASA Astrophysics Data System (ADS)

Tamsitt, Veronica; Drake, Henri; Morrison, Adele; Talley, Lynne; Dufour, Carolina; Gray, Alison; Griffies, Stephen; Mazloff, Matthew; Sarmiento, Jorge; Wang, Jinbo; Weijer, Wilbert

2017-04-01

Upwelling of Atlantic, Indian and Pacific deep waters to the sea surface in the Southern Ocean closes the global overturning circulation and is fundamentally important for oceanic uptake of anthropogenic carbon and heat, nutrient resupply for sustaining oceanic biological production, and the melt rate of ice shelves. Here we go beyond the two-dimensional view of Southern Ocean upwelling, to show detailed Southern Ocean upwelling pathways in three dimensions, using hydrographic observations and particle tracking in high-resolution ocean and climate models. The northern deep waters enter the Antarctic Circumpolar Current (ACC) via narrow southward currents along the boundaries of the three ocean basins, before spiraling southeastward and upward through the ACC. Upwelling is greatly enhanced at five major topographic features, associated with vigorous mesoscale eddy activity. Deep water reaches the upper ocean predominantly south of the southern ACC boundary, with a spatially nonuniform distribution, regionalizing warm water supply to Antarctic ice shelves and the delivery of nutrient and carbon-rich water to the sea surface. The timescale for half of the deep water to upwell from 30°S to the mixed layer is on the order of 60-90 years, which has important implications for the timescale for signals to propagate through the deep ocean. In addition, we quantify the diabatic transformation along particle trajectories, to identify where diabatic processes are important along the upwelling pathways.

Variability of the Somali Current and eddies during the southwest monsoon regimes

NASA Astrophysics Data System (ADS)

Trott, Corinne B.; Subrahmanyam, Bulusu; Murty, V. S. N.

2017-09-01

The meso-scale eddies and currents in the Arabian Sea are analyzed using different satellite observations, Simple Oceanic Data Assimilation (SODA) reanalysis, and Ocean Reanalysis System 4 (ORAS4) from 1993 to 2016 to investigate the impacts of Southwest (SW) Monsoon strength on Somali Current (SC) mesoscale circulations such as the Great Whirl (GW), the Socotra Eddy (SE), the Southern Gyre (SG), and smaller eddies. Increased Ekman pumping during stronger SW monsoons strengthens coastal upwelling along the Somali coast. The Arabian Sea basin-wide anticyclonic circulation and presence of the GW form mesoscale circulation patterns favourable to advection of upwelled waters eastward into the central Arabian Sea. In September, after the SW monsoon winds reach peak strength in July and August, a higher number of discrete anticyclonic eddies with higher (> 20 cm) sea surface height anomalies develop in strong and normal intensity SW monsoon seasons than weaker SW monsoon seasons.

Rapid response to coastal upwelling in a semienclosed bay

NASA Astrophysics Data System (ADS)

Gilcoto, Miguel; Largier, John L.; Barton, Eric D.; Piedracoba, Silvia; Torres, Ricardo; Graña, Rocío.; Alonso-Pérez, Fernando; Villacieros-Robineau, Nicolás.; de la Granda, Francisco

2017-03-01

Bays/estuaries forced by local wind show bidirectional exchange flow. When forced by remote wind, they exhibit unidirectional flow adjustment to coastal sea level. Acoustic Doppler Current Profiler observations over 1 year show that the Ria de Vigo (Iberian Upwelling) responds to coastal wind events with bidirectional exchange flow. The duration of the upwelling and downwelling events, estimated from the current variability, was 3.3 days and 2.6 days, respectively. Vectorial correlations reveal a rapid response to upwelling/downwelling, in which currents lag local wind by <6 h and remote wind by <14 h, less than the Ekman spinup (17.8 h). This rapidity arises from the ria's narrowness (nonrotational local response), equatorward orientation (additive remote and local wind responses), depth greater than the Ekman depth (penetration of shelf circulation into the interior), and vertical stratification (shear reinforcing shelf circulation). Similar rapid responses are expected in other narrow bays where local and remote winds act together and stratification enhances bidirectional flow.

Life cycle strategies of copepods in coastal upwelling zones

NASA Astrophysics Data System (ADS)

Peterson, W.

1998-06-01

Life cycles of copepods of coastal upwelling zones are of the multigenerational type—as many as 10 or more generations may be produced each year, depending upon water temperature, food concentration and length of the upwelling season. Abundant food resources and moderate temperature convey advantages to those copepods living in coastal upwelling zones, however, there is a clear disadvantage in that coastal upwelling zones are highly advective environments. Typically, water circulation patterns are such that surface waters are carried offshore, deeper waters carried onshore and most of the water column over the continental shelf is moving equatorward. The challenge to copepod species that inhabit upwelling systems is life cycle closure—how do eggs, nauplii, juveniles and adults avoid being swept out of these ecosystems in the face of persistent transport out of the system? In this review, I first list the species which dominate coastal upwelling ecosystems then discuss three variations on the multigenerational life cycle scheme that are observed in upwelling systems. The latter part of the review is devoted to discussion of how individuals are retained in the productive continental shelf waters within coastal upwelling ecosystems. The suggestion is made that the only copepod species that successfully achieve life cycle closure in such systems are those that are preadapted to upwelling circulation patterns. Our quantitative understanding of the relative importance of physical factors (such as advection) and biological factors (birth, growth, and mortality) on life cycle strategies and population dynamics is quite rudimentary. It would help our understanding if there were more field studies and more computer modeling studies that focused on seasonal cycles of abundance, development times and vertical distribution of life cycle stages, and measurements of water circulation patterns.

Physical structure and algae community of summer upwelling off eastern Hainan

NASA Astrophysics Data System (ADS)

Xu, H.; Liu, S.; Xie, Q.; Hong, B.; Long, T.

2017-12-01

The upwelling system is the most productive ecosystem along the continental shelf of the northern South China Sea Shelf. It brings nutrient from bottom to surface and blooms biotic community driven by summer monsoon. In this study, we present observed results of physical and biotic community structures during August, 2015 in the upwelling system along Hainan eastern coast, which is one the strongest upwelling systems in the northern South China Sea. By using hydrological data collected by CTD, we found a significant cold water tongue with high salinity which extended from offshore to 100 m isobaths. However, dissolved oxygen (DO) showed a sandwich structure in which high core of DO concentration appeared at the layer from 5 m to 30 m. It possibly was caused by the advection transport of high DO from adjacent area. Basically, this upwelling system was constrained at northern area of 18.8ºN in horizontal due to the weakening summer monsoon in August. In addition, we collected water sample at the upwelling area and measured algae categories and concentration by high performance liquid chromatography (HPLC). Results show the biotic community was dominated by five types of algae mainly, they were diatoms, dinoflagellates, green algae, prokaryotes and prochlorococcus. And different patterns of different algae were demonstrated. In the upwelling area, diatoms and prokaryotes show opposite structures, and more complex pattern for the rest three algae indicating an active biotic community in the upwelling system.

Transient response of the Northwestern Iberian upwelling regime.

PubMed

Ferreira Cordeiro, Nuno Gonçalo; Dubert, Jesus; Nolasco, Rita; Desmond Barton, Eric

2018-01-01

The hydrography and dynamics of NW Iberian margin were explored for July 2009, based on a set of in situ and remote sensing observations. Zonal sections of standard CTD casts, towed CTD (SeaSoar), Acoustic Doppler Current Profilers (ADCP) and Lagrangian surveys were made to characterize cycles of upwelling and relaxation in this region. Two periods of northerly winds, bounded by relaxation periods, were responsible for the formation of an upwelling front extending to the shelf edge. An equatorward flow was quickly set up on the shelf responding to the northerly wind pulses. South of Cape Silleiro, the development and subsequent relaxation of an upwelling event was intensively surveyed in the shelf, following a Lagrangian drifter transported by the upwelling jet. This region is part of an upwelling center extending from Cape Silleiro to Porto, where the surface temperature was colder than the neighboring regions, under upwelling favorable winds. As these winds relaxed, persistent poleward flow developed, originating south of the upwelling center and consisting in an inner-shelf tongue of warm waters. During an event of strong southerly wind, the poleward flow was observed to extend to the whole continental shelf. Although the cruise was executed during summertime, the presence of river-plumes was observed over the shelf. The interaction of the plumes with the circulation on the shelf was also described in terms of coastal convergence and offshore advection. The sampling of the offshore and slope regions showed the presence of the Iberian poleward current offshore and a persistent equatorward flow over the upper slope.

Global climate change and intensification of coastal ocean upwelling.

PubMed

Bakun, A

1990-01-12

A mechanism exists whereby global greenhouse warning could, by intensifying the alongshore wind stress on the ocean surface, lead to acceleration of coastal upwelling. Evidence from several different regions suggests that the major coastal upwelling systems of the world have been growing in upwelling intensity as greenhouse gases have accumulated in the earth's atmosphere. Thus the cool foggy summer conditions that typify the coastlands of northern California and other similar upwelling regions might, under global warming, become even more pronounced. Effects of enhanced upwelling on the marine ecosystem are uncertain but potentially dramatic.

Reconstruction of the Mesoscale Velocity Shear Seaward of Coastal Upwelling Regions from the Refraction of the Surface Wave Field

NASA Technical Reports Server (NTRS)

Flament, Pierre; Graber, Hans C.; Halpern, D.; Holt, B.

1996-01-01

The objective of this project is to study fronts that develop at the boundary between cold water recently upwelled to the surface through Ekman divergence, and warmer surrounding waters. This specific objective was suggested by studying the small scale structure of upwelling fronts (coastal, island, and equatorial) through shipboard surveys and infrared satellite images. Constraints on the shuttle equator crossing imposed by other land sites precluded a coverage of the area targeted in the initial SIR-C proposal, the California Current. The site was then relocated to the Equatorial Pacific upwelling tongue, that can be satisfactorily imaged for a wide range of longitudes of the equator crossing. Some limited data was nevertheless obtained over coastal upwelling off California in 1989, using the JPL AIRSAR in multifrequency mode, and over island upwelling off Hawaii in 1990, using the radar in along-track interferometric mode.

Temporal variability of near-bottom dissolved oxygen during upwelling off central Oregon

NASA Astrophysics Data System (ADS)

Adams, Katherine A.; Barth, John A.; Chan, Francis

2013-10-01

In the productive central-Oregon coastal upwelling environment, wind-driven upwelling, tides, and topographic effects vary across the shelf, setting the stage for varied biogeochemical responses to physical drivers. Current, temperature, salinity, and dissolved oxygen (DO) measurements from three moorings deployed during the upwelling seasons of 2009-2011 off the central-Oregon coast are analyzed over three time bands (interannual, subtidal, tidal) to explore the relationship between mid (70 m) and inner-shelf (15 m) upwelling dynamics and the associated effect on DO. Topographic effects are observed in each time band due to the Heceta and Stonewall Bank complex. Seasonal cumulative hypoxia (DO < 1.4 mL L-1) calculations identify two regions, a well-ventilated inner shelf and a midshelf vulnerable to hypoxia (98 ± 15 days annually). On tidal timescales, along-shelf diurnal (K1) velocities are intensified over the Bank, 0.08 m s-1 compared with 0.03 m s-1 to the north. Interannual variability in the timing of spring and fall transitions, defined using glider-measured continental slope source water temperature, is observed on the midshelf. Interannual source water DO concentrations vary on the order of 0.1 mL L-1. Each spring and summer, DO decline rates are modulated by physical and biological processes. The net observed decrease is about 30% of the expected draw down due to water-column respiration. Physical processes initiate low-oxygen conditions on the shelf through coastal upwelling and subsequently prevent the system via advection and mixing from reaching the potential anoxic levels anticipated from respiration rates alone.

Egg production and hatching success of Calanus chilensis and Acartia tonsa in the northern Chile upwelling zone (23°S), Humboldt Current System

NASA Astrophysics Data System (ADS)

Ruz, Paula M.; Hidalgo, Pamela; Yáñez, Sonia; Escribano, Rubén; Keister, Julie E.

2015-08-01

Oxygen Minimum Zones (OMZ's) are expanding and intensifying as result of climate change, affecting Eastern Boundary Upwelling Systems. Local effects of vertical movements of OMZ's that result from changes in upwelling intensity could reduce or expand the oxygenated surface layer that most zooplanktonic species inhabit in coastal areas. Using the copepods Calanus chilensis and Acartia tonsa as model organisms, an experimental test of the impact of different dissolved oxygen (DO) concentrations (between 0.5 and 5 ml L- 1) on egg production and hatching success was carried out and compared with field estimations of egg production, female and egg abundance in Mejillones Bay (23°S). Abundance of C. chilensis was highly variability and no consistent pattern in egg production and hatching success was found across DO levels, whereas A. tonsa egg production had maximum values between 2.6 and 4.7 ml O2 L- 1 and hatching success was positively correlated with DO (r = 0.75). In the field, temperature was the main factor controlling the dynamics of both species, while Chl-a and DO were also correlated with C. chilensis and A. tonsa, respectively. Principal Component Analysis showed that abundances of both copepods were controlled by temperature, stratification, OMZ depth, and Ekman transport, which together explained more than 70% of the total variance and were the main factors that modulated the populations of C. chilensis and A. tonsa in the upwelling zone of northern Chile (23°S). The differential responses of C. chilensis and A. tonsa to changes in DO concentrations associated with vertical movements of the OMZ suggest that C. chilensis may be better adapted to hypoxic conditions than A. tonsa, however both species are successful and persistent all year-round. We suggest that physiological responses of copepods could be used to evaluate population dynamics affected by the shoaling of OMZ's and the repercussions to trophic food webs of eastern boundary current systems.

Preparing to predict: The Second Autonomous Ocean Sampling Network (AOSN-II) experiment in the Monterey Bay

NASA Astrophysics Data System (ADS)

Ramp, S. R.; Davis, R. E.; Leonard, N. E.; Shulman, I.; Chao, Y.; Robinson, A. R.; Marsden, J.; Lermusiaux, P. F. J.; Fratantoni, D. M.; Paduan, J. D.; Chavez, F. P.; Bahr, F. L.; Liang, S.; Leslie, W.; Li, Z.

2009-02-01

The Autonomous Ocean Sampling Network Phase Two (AOSN-II) experiment was conducted in and offshore from the Monterey Bay on the central California coast during July 23-September 6, 2003. The objective of the experiment was to learn how to apply new tools, technologies, and analysis techniques to adaptively sample the coastal ocean in a manner demonstrably superior to traditional methodologies, and to use the information gathered to improve predictive skill for quantities of interest to end-users. The scientific goal was to study the upwelling/relaxation cycle near an open coastal bay in an eastern boundary current region, particularly as it developed and spread from a coastal headland. The suite of observational tools used included a low-flying aircraft, a fleet of underwater gliders, including several under adaptive autonomous control, and propeller-driven AUVs in addition to moorings, ships, and other more traditional hardware. The data were delivered in real time and assimilated into the Harvard Ocean Prediction System (HOPS), the Navy Coastal Ocean Model (NCOM), and the Jet Propulsion Laboratory implementation of the Regional Ocean Modeling System (JPL/ROMS). Two upwelling events and one relaxation event were sampled during the experiment. The upwelling in both cases began when a pool of cold water less than 13 °C appeared near Cape Año Nuevo and subsequently spread offshore and southward across the bay as the equatorward wind stress continued. The primary difference between the events was that the first event spread offshore and southward, while the second event spread only southward and not offshore. The difference is attributed to the position and strength of meanders and eddies of the California Current System offshore, which blocked or steered the cold upwelled water. The space and time scales of the mesoscale variability were much shorter than have been previously observed in deep-water eddies offshore. Additional process studies are needed to elucidate the dynamics of the flow.

Spatial and temporal variability in coccolithophore abundance and distribution in the NW Iberian coastal upwelling system

NASA Astrophysics Data System (ADS)

Ausín, Blanca; Zúñiga, Diana; Flores, Jose A.; Cavaleiro, Catarina; Froján, María; Villacieros-Robineau, Nicolás; Alonso-Pérez, Fernando; Arbones, Belén; Santos, Celia; de la Granda, Francisco; Castro, Carmen G.; Abrantes, Fátima; Eglinton, Timothy I.; Salgueiro, Emilia

2018-01-01

A systematic investigation of the spatial and temporal variability in coccolithophore abundance and distribution through the water column of the NW Iberian coastal upwelling system was performed. From July 2011 to June 2012, monthly sampling at various water depths was conducted at two parallel stations located at 42° N. Total coccosphere abundance was higher at the outer-shelf station, where warmer, nutrient-depleted waters favoured coccolithophore rather than phytoplanktonic diatom blooms, which are known to dominate the inner-shelf location. In seasonal terms, higher coccosphere and coccolith abundances were registered at both stations during upwelling seasons, coinciding with high irradiance levels. This was typically in conjunction with stratified, nutrient-poor conditions (i.e. relaxing upwelling conditions). However, it also occurred during some upwelling events of colder, nutrient-rich subsurface waters onto the continental shelf. Minimum abundances were generally found during downwelling periods, with unexpectedly high coccolith abundance registered in subsurface waters at the inner-shelf station. This finding can only be explained if strong storms during these downwelling periods favoured resuspension processes, thus remobilizing deposited coccoliths from surface sediments, and hence hampering the identification of autochthonous coccolithophore community structure. At both locations, the major coccolithophore assemblages were dominated by Emiliania huxleyi, small Gephyrocapsa group, Gephyrocapsa oceanica, Florisphaera profunda, Syracosphaera spp., Coronosphaera mediterranea, and Calcidiscus leptoporus. Ecological preferences of the different taxa were assessed by exploring the relationships between environmental conditions and temporal and vertical variability in coccosphere abundance. These findings provide relevant information for the use of fossil coccolith assemblages in marine sediment records, in order to infer past environmental conditions, of particular importance for Paleoceanography. Both E. huxleyi and the small Gephyrocapsa group are proposed as proxies for the upwelling regime with a distinct affinity for different stages of the upwelling event: E. huxleyi was associated with warmer, nutrient-poor and more stable water column (i.e. upwelling relaxation stage) while the small Gephyrocapsa group was linked to colder waters and higher nutrient availability (i.e. early stages of the upwelling event), similarly to G. oceanica. Conversely, F. profunda is suggested as a proxy for the downwelling regime and low-productivity conditions. The assemblage composed by Syracosphaera pulchra, Coronosphaera mediterranea, and Rhabdosphaera clavigera may be a useful indicator of the presence of subtropical waters conveyed northward by the Iberian Poleward Current. Finally, C. leptoporus is proposed as an indicator of warmer, saltier, and oligotrophic waters during the downwelling/winter regime.

Modelling Ecosystem Dynamics of the Oxygen Minimum Zones in the Angola Gyre and the Northern Benguela Upwelling System.

NASA Astrophysics Data System (ADS)

Schmidt, M.; Eggert, A.

2016-02-01

The Angola Gyre and the Northern Benguela Upwelling System are two major oxygen minimum zones (OMZ) of different kind connected by the system of African Eastern Boundary Currents. We discuss results from a 3-dimensional coupled biogeochemical model covering both oxygen-deficient systems. The biogeochemical model component comprises trophic levels up to zooplankton. Physiological properties of organisms are parameterized from field data gained mainly in the course of the project "Geochemistry and Ecology of the Namibian Upwelling System" (GENUS). The challenge of the modelling effort is the different nature of both systems. The Angola Gyre, located in a "shadow zone" of the tropical Atlantic, has a low productivity and little ventilation, hence a long residence time of water masses. In the northern Benguela Upwelling System, trade winds drive an intermittent, but permanent nutrient supply into the euphotic zone which fuels a high coastal productivity, large particle export and high oxygen consumption from dissimilatory processes. In addition to the local processes, oxygen-deficient water formed in the Angola Gyre is one of the source water masses of the poleward undercurrent, which feeds oxygen depleted water into the Benguela system. In order to simulate the oxygen distribution in the Benguela system, both physical transport as well as local biological processes need to be carefully adjusted in the model. The focus of the analysis is on the time scale and the relative contribution of the different oxygen related processes to the oxygen budgets in both the oxygen minimum zones. Although these are very different in both the OMZ, the model is found as suitable to produce oxygen minimum zones comparable with observations in the Benguela and the Angola Gyre as well. Variability of the oxygen concentration in the Angola Gyre depends strongly on organismic oxygen consumption, whereas the variability of the oxygen concentration on the Namibian shelf is governed mostly by pole-ward advection of tropical water masses.

Wind-driven coastal upwelling and westward circulation in the Yucatan shelf

NASA Astrophysics Data System (ADS)

Ruiz-Castillo, Eugenio; Gomez-Valdes, Jose; Sheinbaum, Julio; Rioja-Nieto, Rodolfo

2016-04-01

The wind-driven circulation and wind-induced coastal upwelling in a large shelf sea with a zonally oriented coast are examined. The Yucatan shelf is located to the north of the Yucatan peninsula in the eastern Gulf of Mexico. This area is a tropical shallow body of water with a smooth sloping bottom and is one of the largest shelves in the world. This study describes the wind-driven circulation and wind-induced coastal upwelling in the Yucatan shelf, which is forced by easterly winds throughout the year. Data obtained from hydrographic surveys, acoustic current profilers and environmental satellites are used in the analysis. Hydrographic data was analyzed and geostrophic currents were calculated in each survey. In addition an analytical model was applied to reproduce the currents. The results of a general circulation model were used with an empirical orthogonal function analysis to study the variability of the currents. The study area is divided in two regions: from the 40 m to the 200 m isobaths (outer shelf) and from the coast to the 40 m isobath (inner shelf). At the outer shelf, observations revealed upwelling events throughout the year, and a westward current with velocities of approximately 0.2 m s-1 was calculated from the numerical model output and hydrographic data. In addition, the theory developed by Pedlosky (2007) for a stratified fluid along a sloping bottom adequately explains the current's primary characteristics. The momentum of the current comes from the wind, and the stratification is an important factor in its dynamics. At the inner shelf, observations and numerical model output show a wind-driven westward current with maximum velocities of 0.20 m s-1. The momentum balance in this region is between local acceleration and friction. A cold-water band is developed during the period of maximum upwelling.

Nutrient pumping by submesoscale circulations in the mauritanian upwelling system

NASA Astrophysics Data System (ADS)

Hosegood, P. J.; Nightingale, P. D.; Rees, A. P.; Widdicombe, C. E.; Woodward, E. M. S.; Clark, D. R.; Torres, R. J.

2017-12-01

Observations made within a cold filament in the Mauritanian upwelling system demonstrate that intense submesoscale circulations at the peripheral edges of the filament are likely responsible for anomalously high levels of observed primary productivity by resupplying nutrients to the euphotic zone. Measurements made on the shelf within the recently upwelled water reveal that primary production (PP) of 8.2 gC/m-2 day-1 was supported by nitrate concentrations (NC) of 8 mmol m-3. Towards the front that defined the edge of the filament containing the upwelled water as it was transported offshore, PP dropped to 1.6 gC m-2 day-1 whilst NC dropped to 5.5 mmol m-3. Thus, whilst the observed nutrients on the shelf accounted for 90% of new production, this value dropped to ∼60% near the filament's front after accounting for vertical turbulent fluxes and Ekman pumping. We demonstrate that the N15 was likely to have been supplied at the front by submesoscale circulations that were directly measured as intense vertical velocities ⩾100 m day-1 by a drifting acoustic Doppler current profiler that crossed a submesoscale surface temperature front. At the same time, a recently released tracer was subducted out of the mixed layer within 24 h of release, providing direct evidence that the frontal circulations were capable of accessing the reservoir of nutrients beneath the pycnocline. The susceptibility of the filament edge to submesoscale instabilities was demonstrated by O(1) Rossby numbers at horizontal scales of 1-10 km. The frontal circulations are consistent with instabilities arising from a wind-driven nonlinear Ekman buoyancy flux generated by the persistent northerly wind stress that has a down-front component at the northern edge of the inshore section of the filament. The prevalence of submesoscale instabilities and their associated vertical circulations are proposed to be a key mechanism operating at sub-grid scales and sustaining new production throughout the upwelling system.

Controlling factors of the OMZ in the Arabian Sea

NASA Astrophysics Data System (ADS)

Resplandy, L.; Lévy, M.; Bopp, L.; Echevin, V.; Pous, S.; Sarma, V. V. S. S.; Kumar, D.

2012-05-01

In-situ observations indicate that the Arabian Sea oxygen minimum zone (OMZ) is only weakly influenced by the strong seasonal cycle of ocean dynamic and biogeochemistry forced by the asian monsoon system and it is spatially decorrelated from the coastal upwelling systems where the biological production is the strongest. In this study we examine the factors controlling the seasonality and the spatial distribution of the OMZ in the Arabian Sea using a coupled bio-physical model. We find that the oxygen concentration in the OMZ displays a seasonal cycle with an amplitude of 5-15 % of the annual mean oxygen concentration. The OMZ is ventilated by lateral ventilation along the western boundary current and in the coastal undercurrent along India during the summer monsoon and by coastal downwelling and negative Ekman pumping during the fall intermonsoon and winter monsoon. This ventilation is counterbalanced by strong coastal upwelling and positive Ekman pumping of low oxygen waters at the base of the OMZ during the spring intermonsoon. Although the factors controlling the OMZ seasonality are associated with the men circulation, we find that mesoscale dynamics modulates them by limiting the vertical ventilation during winter and enhancing it through lateral advection during the rest of the year. Processes explaining the establishment and spatial distribution of the OMZ were quantified using a perturbation experiment initialised with no OMZ. As expected, the oxygen depletion is triggered by strong biological activity in central Arabian Sea during winter and in western and eastern boundary coastal upwelling systems during summer. We find that the 3-D ocean dynamic largely controls the spatial distribution of the OMZ. The eastward shift ensues from the northward lateral transport of ventilated waters along the western and eastern coasts and the advection offshore of low oxygen waters formed in the upwelling system.

Diatoms Si uptake capacity drives carbon export in coastal upwelling systems

NASA Astrophysics Data System (ADS)

Abrantes, Fatima; Cermeno, Pedro; Lopes, Cristina; Romero, Oscar; Matos, Lélia; Van Iperen, Jolanda; Rufino, Marta; Magalhães, Vitor

2016-07-01

Coastal upwelling systems account for approximately half of global ocean primary production and contribute disproportionately to biologically driven carbon sequestration. Diatoms, silica-precipitating microalgae, constitute the dominant phytoplankton in these productive regions, and their abundance and assemblage composition in the sedimentary record is considered one of the best proxies for primary production. The study of the sedimentary diatom abundance (SDA) and total organic carbon content (TOC) in the five most important coastal upwelling systems of the modern ocean (Iberia-Canary, Benguela, Peru-Humboldt, California, and Somalia-Oman) reveals a global-scale positive relationship between diatom production and organic carbon burial. The analysis of SDA in conjunction with environmental variables of coastal upwelling systems such as upwelling strength, satellite-derived net primary production, and surface water nutrient concentrations shows different relations between SDA and primary production on the regional scale. On the global scale, SDA appears modulated by the capacity of diatoms to take up silicic acid, which ultimately sets an upper limit to global export production in these ocean regions.

Geochemistry and magnetic sediment distribution at the western boundary upwelling system of southwest Atlantic

NASA Astrophysics Data System (ADS)

Cruz, Anna P. S.; Barbosa, Catia F.; Ayres-Neto, Arthur; Munayco, Pablo; Scorzelli, Rosa B.; Amorim, Nívea Santos; Albuquerque, Ana L. S.; Seoane, José C. S.

2018-02-01

In order to investigate the chemical and magnetic characteristics of sediments of the western boundary upwelling system of Southwest Atlantic we analyzed magnetic susceptibility, grain size distribution, total organic carbon, heavy mineral abundance, Fe associated with Mössbauer spectra, and Fe and Mn of pore water to evaluate the deposition patterns of sediments. Four box-cores were collected along a cross-shelf transect. Brazil Current and coastal plume exert a primary control at the inner and outer shelf cores, which exhibited similar depositional patterns characterized by a high abundance of heavy minerals (mean 0.21% and 0.08%, respectively) and very fine sand, whereas middle shelf cores presented low abundances of heavy minerals (mean 0.03%) and medium silt. The inner shelf was dominated by sub-angular grains, while in middle and outer shelf cores well-rounded grains were found. The increasing Fe3+:Fe2+ ratio from the inner to the outer shelf reflects farther distance to the sediment source. The outer shelf presented well-rounded minerals, indicating abrasive processes as a result of transport by the Brazil Current from the source areas. In the middle shelf, cold-water intrusion of the South Atlantic Central Water contributes to the primary productivity, resulting in higher deposition of fine sediment and organic carbon accumulation. The high input of organic carbon and the decreased grain size are indicative of changes in the hydrodynamics and primary productivity fueled by the western boundary upwelling system, which promotes loss of magnetization due to the induction of diagenesis of iron oxide minerals.

Poleward displacement of coastal upwelling-favorable winds through the 21st century

NASA Astrophysics Data System (ADS)

Rykaczewski, R. R.; Dunne, J. P.; Sydeman, W. J.; Garcia-Reyes, M.; Black, B.; Bograd, S. J.

2016-02-01

Coastal upwelling is a critical factor influencing the biological production, acidification, and deoxygenation of the ocean's major eastern boundary current ecosystems. A leading conceptual hypothesis projects that the winds that induce coastal upwelling will intensify in response to increased land-sea temperature differences associated with anthropogenic global warming. We examine this hypothesis using an ensemble of coupled, ocean-atmosphere models and find limited evidence for intensification of upwelling-favorable winds or atmospheric pressure gradients in response to increasing land-sea temperature differences. However, our analyses reveal consistent latitudinal and seasonal dependencies of projected changes in wind intensity associated with poleward migration of major atmospheric high-pressure cells. Summertime winds near poleward boundaries of climatological upwelling zones are projected to intensify, while winds near equatorward boundaries are projected to weaken. Developing a better understanding of future changes in upwelling winds is essential to identifying portions of the oceans susceptible to increased hypoxia, ocean acidification, and eutrophication under climate change.

The relationship between Arabian Sea upwelling and Indian monsoon revisited

NASA Astrophysics Data System (ADS)

Yi, X.; Hünicke, B.; Tim, N.; Zorita, E.

2015-11-01

Studies based on upwelling indices (sediment records, sea-surface temperature and wind) suggest that upwelling along the western coast of Arabian Sea is strongly affected by the Indian summer monsoon (ISM). In order to examine this relationship directly, we employ the vertical water mass transport produced by the eddy-resolving global ocean simulation STORM driven by meteorological reanalysis over the last 61 years. With its very high spatial resolution (10 km), STORM allows us to identify characteristics of the upwelling system. We analyze the co-variability between upwelling and meteorological and oceanic variables from 1950 to 2010. The analyses reveal high interannual correlations between coastal upwelling and along-shore wind-stress (r=0.73) as well as with sea-surface temperature (r0.83). However, the correlation between the upwelling and the ISM is small and other factors might contribute to the upwelling variability. In addition, no long-term trend is detected in our modeled upwelling time series.

Spatio-Temporal Variation in Effects of Upwelling on the Fatty Acid Composition of Benthic Filter Feeders in the Southern Benguela Ecosystem: Not All Upwelling Is Equal

PubMed Central

McQuaid, Christopher David; Noyon, Margaux

2016-01-01

Variability in mesoscale nearshore oceanographic conditions plays an important role in the distribution of primary production and food availability for intertidal consumers. Advection of nutrient rich waters by upwelling usually allows the proliferation of diatoms, later replaced by dinoflagellates. We examined upwelling effects on the fatty acid (FA) signature of a benthic intertidal filter feeder to identify its response to pulsed variability in food availability. The study took place in two contrasting seasons and at two upwelling and two non-upwelling sites interspersed within the southern Benguela upwelling system of South Africa. We investigated the FA composition of the adductor muscles and gonads of the mussel Mytilus galloprovincialis to assess how FA are apportioned to the different tissues and whether this changes between upwelling and non-upwelling conditions. In situ temperature loggers used to identify upwelling conditions at the four sites indicated that such events occurred only at the upwelling centres and only in summer. Tissues differed strongly, with gonads presenting a higher proportion of essential FAs. This could reflect the faster turnover rate of gonad tissue or preferential retention of specific FA for reproductive purposes. FA composition did not vary as a direct function of upwelling, but there were strong dissimilarities among sites. Upwelling influenced mussel diets at one upwelling site while at the other, the expected signature of upwelling was displaced downstream of the core of upwelling. Condition Index (CI) and Gonad Index (GI) differed among sites and were not influenced by upwelling, with GI being comparable among sites. In addition, FA proportions were consistent among sites, indicating similar food quality and quantity over time and under upwelling and non-upwelling conditions. This suggests that the influence of upwelling on the west coast of South Africa is pervasive and diffuse, rather than discrete; while nearshore retention or advection of upwelled water is critical and site-specific so that the effects of upwelling differ even among sites categorised as upwelling centres. PMID:27570968

Late quaternary time series of Arabian Sea productivity: Global and regional signals

NASA Technical Reports Server (NTRS)

Clemens, Steven C.; Prell, W. L.; Murray, D. W.

1992-01-01

Modern annual floral and faunal production in the northwest Arabian Sea derives primarily from upwelling induced by strong southwest winds during June, July, and August. Indian Ocean summer monsoon winds are, in turn, driven by differential heating between the Asian continent and the Indian ocean to the south. This differential heating produces a strong pressure gradient resulting in southwest monsoon winds and both coastal and divergent upwelling off the Arabian Peninsula. Over geologic time scales (10(exp 4) to 10(exp 6) years), monsoon wind strength is sensitive to changes in boundary conditions which influence this pressure gradient. Important boundary conditions include the seasonal distribution of solar radiation, global ice volume, Indian Ocean sea surface temperature, and the elevation and albedo of the Asian continent. To the extent that these factors influence monsoon wind strength, they also influence upwelling and productivity. In addition, however, productivity associated with upwelling can be decoupled from the strength of the summer monsoon winds via ocean mechanisms which serve to inhibit or enhance the nutrient supply in the intermediate waters of the Indian Ocean, the source for upwelled waters in the Arabian Sea. To differentiate productivity associated with wind-induced upwelling from that associated with other components of the system such as nutrient sequestering in glacial-age deep waters, we employ a strategy which monitors independent components of the oceanic and atmospheric subsystems. Using sediment records from the Owen Ridge, northwest Arabian Sea, we monitor the strength of upwelling and productivity using two independent indicators, percent G. bulloides and opal accumulation. We monitor the strength of southwest monsoon winds by measuring the grain-size of lithogenic dust particles blown into the Arabian Sea from the surrounding deserts of the Somali and Arabian Peninsulas. Our current hypothesis is that the variability associated with the 41 kyr power in the G. bulloides and opal accumulation records derive from nutrient availability in the intermediate waters which are upwelled via monsoon winds. This hypothesis is testable by comparison with Cd records of intermediate and deep waters of the Atlantic and Indian Ocean.

The ichthyoplankton assemblage of the Canaries-African Coastal Transition Zone: A review

NASA Astrophysics Data System (ADS)

Rodriguez, J. M.; Moyano, M.; Hernandez-Leon, S.

2009-12-01

In this paper we review information on the ichthyoplankton assemblage of the Canaries-African Coastal Transition Zone (C-ACTZ). This CTZ shows the singularity that the Canary Archipelago interrupts the main flow of the Canary Current and Trade Winds, introducing large mesoscale variability, in the form of island warm wakes and cyclonic and anticyclonic eddies downstream of the islands. Besides, upwelling filaments stretch towards the archipelago from the African coastal upwelling, transporting phytoplankton, zooplankton and fish larvae. They also interact with eddies shed from the islands to exchange water properties and biogenic material. All these mesoscale features influence the composition, structure, abundance and distribution of the larval fish community (LFC) of the region. The Canary Current (CC) and eddies shed from the islands drag larvae of island neritic fish species into the oceanic region and contribute, along warm wakes, to the horizontal distribution of fish larvae. Upwelling and upwelling filaments transport larvae of African neritic species into the oceanic region. These larvae dominate the LFC and account for the relatively high average larval fish abundance found in the C-ACTZ during the summer upwelling season. Filaments originated in the region of Cape Juby-Cape Bojador are entrained around a quasi-permanent cyclonic eddy, trapped between Gran Canaria Island and the African coast, forming a system through which most of the African neritic larvae may return to the African shelf. However, some larvae reach the eastern islands of the Canary archipelago and they may be spread all over the neritic region of the archipelago by eddies shed from the islands. Also in summer, the distribution of the LFC of the C-ACTZ is vertically stratified and fish larvae seem to carry out little or not diel vertical migration. Overall, this study highlights the strong relationship between mesoscale oceanographic processes and the LFC in the C-ACTZ.

Evaluation and application of the ROMS 1-way embedding procedure to the central california upwelling system

NASA Astrophysics Data System (ADS)

Penven, Pierrick; Debreu, Laurent; Marchesiello, Patrick; McWilliams, James C.

What most clearly distinguishes near-shore and off-shore currents is their dominant spatial scale, O (1-30) km near-shore and O (30-1000) km off-shore. In practice, these phenomena are usually both measured and modeled with separate methods. In particular, it is infeasible for any regular computational grid to be large enough to simultaneously resolve well both types of currents. In order to obtain local solutions at high resolution while preserving the regional-scale circulation at an affordable computational cost, a 1-way grid embedding capability has been integrated into the Regional Oceanic Modeling System (ROMS). It takes advantage of the AGRIF (Adaptive Grid Refinement in Fortran) Fortran 90 package based on the use of pointers. After a first evaluation in a baroclinic vortex test case, the embedding procedure has been applied to a domain that covers the central upwelling region off California, around Monterey Bay, embedded in a domain that spans the continental U.S. Pacific Coast. Long-term simulations (10 years) have been conducted to obtain mean-seasonal statistical equilibria. The final solution shows few discontinuities at the parent-child domain boundary and a valid representation of the local upwelling structure, at a CPU cost only slightly greater than for the inner region alone. The solution is assessed by comparison with solutions for the whole US Pacific Coast at both low and high resolutions and to solutions for only the inner region at high resolution with mean-seasonal boundary conditions.

Optimal Environmental Conditions and Anomalous Ecosystem Responses: Constraining Bottom-up Controls of Phytoplankton Biomass in the California Current System

PubMed Central

Jacox, Michael G.; Hazen, Elliott L.; Bograd, Steven J.

2016-01-01

In Eastern Boundary Current systems, wind-driven upwelling drives nutrient-rich water to the ocean surface, making these regions among the most productive on Earth. Regulation of productivity by changing wind and/or nutrient conditions can dramatically impact ecosystem functioning, though the mechanisms are not well understood beyond broad-scale relationships. Here, we explore bottom-up controls during the California Current System (CCS) upwelling season by quantifying the dependence of phytoplankton biomass (as indicated by satellite chlorophyll estimates) on two key environmental parameters: subsurface nitrate concentration and surface wind stress. In general, moderate winds and high nitrate concentrations yield maximal biomass near shore, while offshore biomass is positively correlated with subsurface nitrate concentration. However, due to nonlinear interactions between the influences of wind and nitrate, bottom-up control of phytoplankton cannot be described by either one alone, nor by a combined metric such as nitrate flux. We quantify optimal environmental conditions for phytoplankton, defined as the wind/nitrate space that maximizes chlorophyll concentration, and present a framework for evaluating ecosystem change relative to environmental drivers. The utility of this framework is demonstrated by (i) elucidating anomalous CCS responses in 1998–1999, 2002, and 2005, and (ii) providing a basis for assessing potential biological impacts of projected climate change. PMID:27278260

Multifarious anchovy and sardine regimes in the Humboldt Current System during the last 150 years.

PubMed

Salvatteci, Renato; Field, David; Gutiérrez, Dimitri; Baumgartner, Tim; Ferreira, Vicente; Ortlieb, Luc; Sifeddine, Abdel; Grados, Daniel; Bertrand, Arnaud

2018-03-01

The Humboldt Current System (HCS) has the highest production of forage fish in the world, although it is highly variable and the future of the primary component, anchovy, is uncertain in the context of global warming. Paradigms based on late 20th century observations suggest that large-scale forcing controls decadal-scale fluctuations of anchovy and sardine across different boundary currents of the Pacific. We develop records of anchovy and sardine fluctuations since 1860 AD using fish scales from multiple sites containing laminated sediments and compare them with Pacific basin-scale and regional indices of ocean climate variability. Our records reveal two main anchovy and sardine phases with a timescale that is not consistent with previously proposed periodicities. Rather, the regime shifts in the HCS are related to 3D habitat changes driven by changes in upwelling intensity from both regional and large-scale forcing. Moreover, we show that a long-term increase in coastal upwelling translates via a bottom-up mechanism to top predators suggesting that the warming climate, at least up to the start of the 21st century, was favorable for fishery productivity in the HCS. © 2017 John Wiley & Sons Ltd.

Potential new production in two upwelling regions of the western Arabian Sea: Estimation and comparison

NASA Astrophysics Data System (ADS)

Liao, Xiaomei; Zhan, Haigang; Du, Yan

2016-07-01

Using satellite-derived and in situ data, the wind-driven potential new production (nitrate supply) for the 300 km wide coastal band in two upwelling regions of the western Arabian Sea (AS) during the southwest monsoon is estimated. The upward nitrate flux to the euphotic zone is generally based on the physical processes of coastal transport (Ekman transport and geostrophic transport) and offshore Ekman pumping. The coastal geostrophic current in the western AS influences the upwelling intensity and latitudinal distributions of nitrate supply. The Oman and Somalia upwelling regions have similar level of potential new production (nitrate supply) during the summer monsoon, while the satellite estimates of primary production off Oman are 2 times greater than those off Somalia. The much higher potential f-ratio in the Somalia upwelling region indicates that the primary production could be limited by availability of other macronutrients (e.g., silicate). The correlation analysis of the primary production and the aerosol optical thickness shows that the Oman upwelling region displays a stronger coupling between the atmospheric deposition and the phytoplankton abundance. The high summertime dust levels in the atmosphere are suggested to contribute to the high primary production in the Oman upwelling region.

Intensification of Chile-Peru upwelling under climate change: diagnosing the impact of natural and anthropogenic forcing from the IPSL-CM5 model.

NASA Astrophysics Data System (ADS)

Jebri, B.; Khodri, M.; Gastineau, G.; Echevin, V.; Thiria, S.

2017-12-01

Upwelling is critical to the biological production, acidification, and deoxygenation of the ocean's major eastern boundary current ecosystems. A conceptual hypothesis suggests that the winds that favour coastal upwelling intensify with anthropogenic global warming due to increased land-sea temperature contrast. We examine this hypothesis for the dynamics of the Peru-Chile upwelling using a set of four large ensembles of coupled, ocean-atmosphere model simulations with the IPSL model covering the 1940-2014 period. In one large ensemble we prescribe the standard CMIP5 greenhouse gas (GHG) concentrations, anthropogenic aerosol, ozone and volcanic forcings, following the historical experiments through 2005 and RCP8.5 from 2006-2014, while the other ensembles consider separately the GHG, ozone and volcanic forcings. We find evidence for intensification of upwelling-favourable winds with however little evidence of atmospheric pressure gradients in response to increasing land-sea temperature differences. Our analyses reveal poleward migration and intensification of the South Pacific Anticyclone near poleward boundaries of climatological Peruvian and Chilean upwelling zones. This contribution further investigates the physical mechanisms for the Peru-Chile upwelling intensification and the relative role of natural and anthropogenic forcings.

Particle Fluxes and Bulk Geochemical Characterization of the Cabo Frio Upwelling System in Southeastern Brazil: Sediment Trap Experiments between Spring 2010 and Summer 2012.

PubMed

Albuquerque, Ana Luiza S; Belém, André L; Zuluaga, Francisco J B; Cordeiro, Livia G M; Mendoza, Ursula; Knoppers, Bastiaan A; Gurgel, Marcio H C; Meyers, Philip A; Capilla, Ramsés

2014-05-14

Physical and biogeochemical processes in continental shelves act synergistically in both transporting and transforming suspended material, and ocean dynamics control the dispersion of particles by the coastal zone and their subsequent mixing and dilution within the shelf area constrained by oceanic boundary currents, followed by their gradual settling in a complex sedimentary scenario. One of these regions is the Cabo Frio Upwelling System located in a significantly productive area of Southeastern Brazil, under the control of the nutrient-poor western boundary Brazil Current but also with a wind-driven coastal upwelling zone, inducing cold-water intrusions of South Atlantic Central Water on the shelf. To understand these synergic interactions among physical and biogeochemical processes in the Cabo Frio shelf, a series of four experiments with a total of 98 discrete samples using sediment traps was performed from November 2010 to March 2012, located on the 145 m isobath on the edge of the continental shelf. The results showed that lateral transport might be relevant in some cases, especially in deep layers, although no clear seasonal cycle was detected. Two main physical-geochemical coupling scenarios were identified: singular downwelling events that can enhance particles fluxes and are potentially related to the Brazil Current oscillations; and events of significant fluxes related to the intrusion of the 18°C isotherm in the euphotic zone. The particulate matter settling in the Cabo Frio shelf area seems to belong to multiple marine and terrestrial sources, in which both Paraiba do Sul River and Guanabara Bay could be potential land-sources, although the particulate material might subject intense transformation (diagenesis) during its trajectory to the shelf edge.

Mesoscale Structure of Bio-Optical Properties Within the Northern California Current System, 2000-2002

NASA Astrophysics Data System (ADS)

Cowles, T. J.; Barth, J. A.; Wingard, C. E.; Desiderio, R. A.; Letelier, R. M.; Pierce, S. D.

2002-12-01

Mesoscale mapping of the hydrographic and bio-optical properties of the Northern California Current System was conducted during spring and summer 2000, 2001, and 2002 off the Oregon coast. A towed, undulating vehicle carried a CTD, two fluorometers, a multi-wavelength absorption and attenuation meter (ac-9), and a PAR sensor. In addition, an ac-9 and a Fast Repetition Rate fluorometer (FRRf) collected bio-optical data on surface waters throughout the mesoscale surveys. Multiple onshore-offshore transect lines provided repeated crossings of velocity jet and frontal boundaries, and allowed resolution of physical and bio-optical parameters on horizontal scales of 1km or less and on vertical scales of 1-2m. Our multi-year results permit assessment of the linkages and the degree of coupling between physical and bio-optical patterns during strong upwelling and strong downwelling events, as well as during low-wind relaxation intervals. The location of the coastal jet and the upwelling front fluctuated considerably under the variable forcing regime, with more extensive mesoscale structure in all parameters in late summer relative to spring, as current meanders developed around subsurface topography (Heceta Bank) and moved offshore near Cape Blanco. Sharp horizontal gradients in autotrophic biomass were observed across the boundaries of the coastal jet and the upwelling front, with chlorophyll levels often in excess of 5-10 mg m-3 on the inshore side of the fronts. Horizontal gradients also were observed in the spectral slope of attenuation and dissolved absorption as well as in the physiological properties of the autotrophic assemblages (as determined with FRRf). Details of the spatial correlations of physical and bio-optical parameters will be presented.

Wind, Circulation, and Topographic Effects on Alongshore Phytoplankton Variability in the California Current

NASA Astrophysics Data System (ADS)

Fiechter, Jerome; Edwards, Christopher A.; Moore, Andrew M.

2018-04-01

A physical-biogeochemical model is used to produce a retrospective analysis at 3-km resolution of alongshore phytoplankton variability in the California Current during 1988-2010. The simulation benefits from downscaling a regional circulation reanalysis, which provides improved physical ocean state estimates in the high-resolution domain. The emerging pattern is one of local upwelling intensification in response to increased alongshore wind stress in the lee of capes, modulated by alongshore meanders in the geostrophic circulation. While stronger upwelling occurs near most major topographic features, substantial increases in phytoplankton biomass only ensue where local circulation patterns are conducive to on-shelf retention of upwelled nutrients. Locations of peak nutrient delivery and chlorophyll accumulation also exhibit interannual variability and trends noticeably larger than the surrounding shelf regions, thereby suggesting that long-term planktonic ecosystem response in the California Current exhibits a significant local scale (O(100 km)) alongshore component.

Influence of Coastal Upwelling on SST Trends along the South Coast of Java

PubMed Central

Varela, R.; Santos, F.; Gómez-Gesteira, M.; Álvarez, I.; Costoya, X.; Días, J. M.

2016-01-01

The south coast of Java has warmed at a much lower rate than adjacent ocean locations over the last three decades (1982–2015). This behavior can be observed during the upwelling season (July-October) and it is especially patent in August and September when upwelling attains the highest values. Although different warming rates (ocean-coast) had been previously observed in other areas around the world, this behavior was always linked to situations where upwelling increased or remained unchanged. South Java warming is observed at ocean locations and cooling near shore but under a scenario of decreasing upwelling (~30% in some cases). The origin of coastal cooling is due to changes in the vertical structure of the water column. A vein of subsurface water, which has cooled at a rate higher than 0.3°C per decade, is observed to enter from the northwestern part of the study area following the South Java Current. This water only manifests at surface near coast, where it is pumped up by coastal upwelling. PMID:27606676

Response of O2 and pH to ENSO in the California Current System in a high-resolution global climate model

NASA Astrophysics Data System (ADS)

Turi, Giuliana; Alexander, Michael; Lovenduski, Nicole S.; Capotondi, Antonietta; Scott, James; Stock, Charles; Dunne, John; John, Jasmin; Jacox, Michael

2018-02-01

Coastal upwelling systems, such as the California Current System (CalCS), naturally experience a wide range of O2 concentrations and pH values due to the seasonality of upwelling. Nonetheless, changes in the El Niño-Southern Oscillation (ENSO) have been shown to measurably affect the biogeochemical and physical properties of coastal upwelling regions. In this study, we use a novel, high-resolution global climate model (GFDL-ESM2.6) to investigate the influence of warm and cold ENSO events on variations in the O2 concentration and the pH of the CalCS coastal waters. An assessment of the CalCS response to six El Niño and seven La Niña events in ESM2.6 reveals significant variations in the response between events. However, these variations overlay a consistent physical and biogeochemical (O2 and pH) response in the composite mean. Focusing on the mean response, our results demonstrate that O2 and pH are affected rather differently in the euphotic zone above ˜ 100 m. The strongest O2 response reaches up to several hundreds of kilometers offshore, whereas the pH signal occurs only within a ˜ 100 km wide band along the coast. By splitting the changes in O2 and pH into individual physical and biogeochemical components that are affected by ENSO variability, we found that O2 variability in the surface ocean is primarily driven by changes in surface temperature that affect the O2 solubility. In contrast, surface pH changes are predominantly driven by changes in dissolved inorganic carbon (DIC), which in turn is affected by upwelling, explaining the confined nature of the pH signal close to the coast. Below ˜ 100 m, we find conditions with anomalously low O2 and pH, and by extension also anomalously low aragonite saturation, during La Niña. This result is consistent with findings from previous studies and highlights the stress that the CalCS ecosystem could periodically undergo in addition to impacts due to climate change.

Coastal counter-currents setup patterns in the Gulf of Cadiz

NASA Astrophysics Data System (ADS)

Relvas, P.; Juniór, L.; Garel, E.; Drago, T.

2017-12-01

Alongshore coastal counter-currents (CCC) are frequent features of Eastern Boundary Upwelling Systems, where they temporally alternate with upwelling driven jets of opposite direction. Along the northern margin of the Gulf of Cadiz inner shelf, these CCCs are oriented poleward (eastward) and responsible for sharp temperature increases during the upwelling season, along with potential decline in water quality at the coast. This research is based on a multi-year ADCP velocity time-series (2008-2017), recorded at a single location (23 m water depth) over 13 deployments up to 3 months-long. The analysis focuses on the water column alongshore velocities during current inversions (i.e., the transition from equatorward upwelling jets to poleward CCCs). A set of parameters were derived from the flow structure to identify distinct types of inversions and to hypothesize about their driving mechanisms. Results show that 77% of the inversions start near the bed, propagating then to the upper layers. The bottom layer also changes direction before the surface layer for most events (71%). The vertical shear in this case is one order of magnitude greater than in the (less frequent) opposite situation. No seasonal variability is observed in the CCC occurrences. However, the parameters analysed in this study suggest different types of inversion between winter and summer. In winter, inversions are well defined (low variability), with similar patterns near the surface and bed layers as a result of a strong barotropic component. In summer the inversion patterns are more variable. In particular, the upper and bed layers are often importantly decoupled during inversions, indicating the strengthening of baroclinicity. A categorization of inversions events is proposed based on cross-correlation and multi-variable analyses of the developed parameters. Various types of inversion are obtained, suggesting that CCCs are driven by different forcings that may act separately or jointly.

Biogenic sedimentation beneath the California Current system for the past 30 kyr and its paleoceanographic significance

USGS Publications Warehouse

Gardner, J.V.; Dean, W.E.; Dartnell, P.

1997-01-01

A north-south transect of 17 cores was constructed along the eastern boundary of the California Current system from 33?? to 42?? N to investigate the changes in biogenic sedimentation over the past 30 kyr. Percentages and mass accumulation rates of CaCO3, Corg, and biogenic opal were assembled at 500 to 1000 years/sample to provide relatively high resolution. Time-space maps reveal a complex pattern of changes that do not follow a simple glacial-interglacial two-mode model. Biogenic sedimentation shows responses that are sometimes time-transgressive and sometimes coeval, and most of the responses show more consistency within a limited geographic area than any temporal consistency. Reconstructed conditions during late oxygen isotope stage 3 were more like early Holocene conditions than any other time during the last 30 kyr. Coastal upwelling and productivity during oxygen isotope stage 3 were relatively strong along the central California margin but were weak along the northern California margin. Precipitation increased during the last glacial interval in the central California region, and the waters of the southern California margin had relatively low productivity. Productivity on the southern Oregon margin was relatively low at the beginning of the last glacial interval, but by about 20 ka, productivity in this area significantly increased. This change suggests that the center of the divergence of the West Wind Drift shifted south at this time. The end of the last glacial interval was characterized by increased productivity in the southern California margin and increased upwelling along the central California margin but upwelling remained weak along the northern California margin. A sudden (<300 years) decrease in CaCO3, Corg, and biogenic opal occurred at 13 ka. The changes suggest a major reorientation of the atmospheric circulation in the North Pacific and western North America and the establishment of a strong seasonality in the central California region. A carbonate preservation event occurred at 10 ka that appears to reflect the uptake of CO2 by the terrestrial biosphere as the northern latitudes were reforested following retreat of the glaciers. The Holocene has been a period of relatively high productivity in the southern California margin, relatively strong coastal upwelling along the central California margin, relatively weak upwelling along the northern California margin, and the northward migration of the divergence zone of the West Wind Drift.

Pliocene Warm Period Upwelling in the Southern Benguela Region

NASA Astrophysics Data System (ADS)

Petrick, B. F.; McClymont, E.; Felder, S.; Leng, M. J.; Rosell Mele, A.; Rueda, G.

2014-12-01

The mid-Pliocene has been proposed as a possible analogue for understanding future climate change and testing climate models. Previous work has shown that during the Pliocene the major upwelling systems were relatively warm, and thus either inactive, contracted, or upwelling warmer waters than present. Here we examine evidence from a core site located on the margins of the modern Benguela upwelling system, to test whether the upwelling cells had migrated or contracted relative to present during the Pliocene. We applied several organic geochemistry proxies and foraminiferal analyses to reconstruct the Pliocene history of ODP site 1087 (31º28'S, 15º19'E, 1374m water depth), including the UK37' index and TEX86 index (for reconstructing sea surface temperatures), chlorins (for estimating primary productivity) and planktonic foraminifera assemblages (for inferring water mass changes). These proxies show that between 3.5 and 3.0 Ma the southern Benguela region was significantly cooler than the northern Benguela region, the latter where the main upwelling cells are found today. Coupled with higher primary production, a shift in planktonic foraminifera assemblage, and an offset between the UK37' index and TEX86 index, we infer that more extensive upwelling was present in the southern Benguela region during the Pliocene. We infer that the main Benguela upwelling cells had shifted southward relative to today, as a result of changes in the local wind field. We find evidence for pronounced cooling and a shift in the planktonic foraminifera assemblage during the M2 and KM2 glacial stages, showing a sensitivity of Benguela upwelling to these short-lived climate events.

Intensification and spatial homogenization of coastal upwelling under climate change.

PubMed

Wang, Daiwei; Gouhier, Tarik C; Menge, Bruce A; Ganguly, Auroop R

2015-02-19

The timing and strength of wind-driven coastal upwelling along the eastern margins of major ocean basins regulate the productivity of critical fisheries and marine ecosystems by bringing deep and nutrient-rich waters to the sunlit surface, where photosynthesis can occur. How coastal upwelling regimes might change in a warming climate is therefore a question of vital importance. Although enhanced land-ocean differential heating due to greenhouse warming has been proposed to intensify coastal upwelling by strengthening alongshore winds, analyses of observations and previous climate models have provided little consensus on historical and projected trends in coastal upwelling. Here we show that there are strong and consistent changes in the timing, intensity and spatial heterogeneity of coastal upwelling in response to future warming in most Eastern Boundary Upwelling Systems (EBUSs). An ensemble of climate models shows that by the end of the twenty-first century the upwelling season will start earlier, end later and become more intense at high but not low latitudes. This projected increase in upwelling intensity and duration at high latitudes will result in a substantial reduction of the existing latitudinal variation in coastal upwelling. These patterns are consistent across three of the four EBUSs (Canary, Benguela and Humboldt, but not California). The lack of upwelling intensification and greater uncertainty associated with the California EBUS may reflect regional controls associated with the atmospheric response to climate change. Given the strong linkages between upwelling and marine ecosystems, the projected changes in the intensity, timing and spatial structure of coastal upwelling may influence the geographical distribution of marine biodiversity.

Characterizing the Phytoplankton Community of the South China Sea

NASA Astrophysics Data System (ADS)

Aleman, M.; Subramaniam, A.; Hay, I.

2016-12-01

The South China Sea (SCS) is a semi-enclosed tropical basin that receives nutrients from two main sources: coastal upwelling and river runoff from the surrounding countries. The southwest (SW) summer monsoon that occurs between March and September drives upwelling off the coast of Vietnam, a rarity compared to most upwelling systems that are driven by eastern boundary current systems. The upwelling in the SCS and the intensity of the SW monsoon are sensitive to climate variability and are affected by phenomenon such as El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). The size and location of the Mekong River plume also varies from year to year due to the variation in rainfall and wind strength of the monsoon. The riverine input is also influenced by anthropogenic activity such as agriculture, damming, and land-use changes. Different nutrients are supplied from these two main sources and in different quantities, and affect the structure of the phytoplankton community. Phytoplankton comprise the base of the food web, supporting the growth of higher organisms and ultimately support fisheries. We need to understand how the supply of different nutrients alters the phytoplankton community of the SCS. We sampled 22 stations along the coast of Vietnam aboard the R/V Falkor of the Schmidt Ocean Institute during the pre-monsoon season. High performance liquid chromatography (HPLC) and flow cytometric techniques will be used to characterize the phytoplankton community. The relationship between the different water masses, nutrient sources, and phytoplankton community found in the SCS will be presented.

Upwelling and downwelling induced by mesoscale circulation in the DeSoto Canyon region

NASA Astrophysics Data System (ADS)

Nguyen, T. T.; Chassignet, E.; Morey, S. L.; Dukhovskoy, D. S.

2014-12-01

Ocean dynamics are complex over irregular topography areas, and the northeastern Gulf of Mexico, specifically the DeSoto Canyon region, is a challenge for modelers and oceanographers. Vertical movement of waters, especially upwelling, is observed to take place over the canyon's head and along the coast; however, it is not well understood. We focus on upwelling/downwelling processes induced by the Loop Current and its associated eddy field using multi-decadal Hybrid Coordinate Ocean Model simulations. The Loop Current, part of the Gulf Stream, can develop northward into the Gulf through the Yucatan Channel and exit through the Florida Straits. It can reach the continental slope of the study domain and directly depress the isopycnals. Cyclonic eddies in front of the Loop Current also induce upwelling underneath. On the other hand, the Loop Current sometimes impinges on the West Florida Shelf and generates a high pressure disturbance, which travels northward along the shelf into the study region. Consequently, large-scale downwelling occurs across the continental slopes. Our analysis of sea surface height shows that the Loop Current pressure disturbance tends to propagate along the shallow isobaths of 100 to 300 m in the topographic wave direction from south of the West Florida Shelf to the Mississippi Delta. In addition, after shedding a large anticyclonic eddy, the Loop Current retracts southward and can touch the southeastern corner of the West Florida Shelf. This can result in a higher pressure disturbance, and therefore stronger large-scale downwelling in the DeSoto Canyon region.

Sr/Ca and Mg/Ca in Glycymeris glycymeris (Bivalvia) shells from the Iberian upwelling system: Ontogeny and environmental control

NASA Astrophysics Data System (ADS)

Freitas, Pedro; Richardson, Christopher; Chenery, Simon; Monteiro, Carlos; Butler, Paul; Reynolds, David; Scourse, James; Gaspar, Miguel

2017-04-01

Bivalve shells have a great potential as high-resolution geochemical proxy archives of marine environmental conditions. In addition, sclerochronology of long-lived bivalve species (e.g. Arctica islandica) provides a timeline of absolutely dated shell material for geochemical analysis that can extend into the past beyond the lifetime of single individuals through the use of replicated crossmatched centennial to millennial chronologies. However, the interpretation of such records remains extremely challenging and complex, with multiple environmental and biological processes affecting element incorporation in the shell (e.g. crystal fabrics, organic matrix, biomineralization mechanisms and physiological processes). As a result, the effective use of bivalve shell elemental/Ca ratios as palaeoenvironmental proxies has been limited, often to species-specific applications or applications restricted to particular environmental settings. The dog-cockle, Glycymeris glycymeris, is a relatively long-lived bivalve (up to 200 years) that occurs in coarse-grained subtidal sediments of coastal shelf seas of Europe and North West Africa. Glycymeris glycymeris shells provide a valuable, albeit not fully explored, archive to reconstruct past environmental variability in an area lacking sclerochronological studies due to the rarity of long-lived bivalves and lack of coral reefs. In this study, we evaluate the potential of Sr/Ca and Mg/Ca ratios in G. glycymeris shells as geochemical proxies of upwelling conditions in the Iberian Upwelling System, the northern section of the Canary Current Eastern Boundary Upwelling System. Sr/Ca and Mg/Ca generally co-varied significantly and a clear ontogenetic, non-environmental related change in Sr/Ca and Ba/Ca variability was observed. High Sr/Ca and Mg/Ca ratios in older shells (> 10 years old) were found to be associated with the occurrence of growth lines deposited during the winter reduction in shell growth. Nevertheless, Sr/Ca and Mg/Ca variation in older shells was synchronous with contemporary environmental conditions, i.e. upwelling intensity and salinity. The use of Sr or Mg in G. glycymeris shells as valid geochemical environmental proxies in the Iberian Upwelling System remains complex and requires further research to unravel environmental and physiological/biomineralization controls. This study was financed by the Portuguese Fundação para a Ciência e Tecnologia (FCT) GLYCY Project (contract PTDC/AAC-CLI/118003/2010) and a sabbatical grant to PSF (Ref: SFRH/BSAB/127786/2016), co-supported by POCH and the European Social Fund. Funding for consumable costs was provided by Bangor University.

The relationship between Arabian Sea upwelling and Indian Monsoon revisited in a high resolution ocean simulation

NASA Astrophysics Data System (ADS)

Yi, Xing; Hünicke, Birgit; Tim, Nele; Zorita, Eduardo

2018-01-01

Studies based on sediment records, sea-surface temperature and wind suggest that upwelling along the western coast of Arabian Sea is strongly affected by the Indian summer Monsoon. We examine this relationship directly in an eddy-resolving global ocean simulation STORM driven by atmospheric reanalysis over the last 61 years. With its very high spatial resolution (10 km), STORM allows us to identify characteristics of the upwelling system. We analyse the co-variability between upwelling and meteorological and oceanic variables from 1950 to 2010. The analysis reveals high interannual correlations between coastal upwelling and along-shore wind-stress (r = 0.73) as well as with sea-surface temperature (r = -0.83). However, the correlation between the upwelling and the Monsoon is small. We find an atmospheric circulation pattern different from the one that drives the Monsoon as the main modulator of the upwelling variability. In spite of this, the patterns of temperature anomalies that are either linked to Arabian Sea upwelling or to the Monsoon are spatially quite similar, although the physical mechanisms of these links are different. In addition, no long-term trend is detected in our modelled upwelling in the Arabian Sea.

Benguela upwelling response during intervals of global climate transition

NASA Astrophysics Data System (ADS)

Shrivastava, Ankush; Sinha, Devesh; Singh, Ashutosh; Ramesh, Rengaswamy

2017-04-01

In the present study sedimentary records from the southeast Atlantic ocean were used for reconstructing the variability of Benguela upwelling system as well as the Interoceanic exchange between Indian and Atlantic Oceans during the critical intervals. Planktic foraminiferal assemblage data revealed diminished upwelling in the Benguela upwelling region during the Pliocene warm interval (3.7-3 Ma) which is in contrast to the model reconstructions by Wang et al., 2015 proposing intensification of upwelling with projected future warming. Gradual intensification of Benguela upwelling was interpreted during the Pliocene - Pleistocene transition (3-2.5 Ma). Enhanced Benguela upwelling during the Northern Hemisphere Glaciation supposed to have played a major role in the drawdown of atmospheric carbon dioxide after Pliocene warmth interval (3.7-3 Ma). Enhanced Benguela upwelling also occurred during Mid- Pleistocene transition (1-0.7 Ma). Reduced interoceanic exchange has been identified between Indian and Atlantic ocean during Northern Hemisphere glaciation (2.5- 2 Ma) and Mid-Pleistocene transition (1- 0.7 Ma). Equatorward migration of subtropical fronts during these two intervals was probably responsible for the reduced interoceanic exchange. Keywords: Pliocene-Pleistocene transition, Mid- Pleistocene transition, Benguela upwelling, Interoceanic exchange

Climate change and decadal shifts in the phenology of larval fishes in the California Current ecosystem

PubMed Central

Asch, Rebecca G.

2015-01-01

Climate change has prompted an earlier arrival of spring in numerous ecosystems. It is uncertain whether such changes are occurring in Eastern Boundary Current Upwelling ecosystems, because these regions are subject to natural decadal climate variability, and regional climate models predict seasonal delays in upwelling. To answer this question, the phenology of 43 species of larval fishes was investigated between 1951 and 2008 off southern California. Ordination of the fish community showed earlier phenological progression in more recent years. Thirty-nine percent of seasonal peaks in larval abundance occurred earlier in the year, whereas 18% were delayed. The species whose phenology became earlier were characterized by an offshore, pelagic distribution, whereas species with delayed phenology were more likely to reside in coastal, demersal habitats. Phenological changes were more closely associated with a trend toward earlier warming of surface waters rather than decadal climate cycles, such as the Pacific Decadal Oscillation and North Pacific Gyre Oscillation. Species with long-term advances and delays in phenology reacted similarly to warming at the interannual time scale as demonstrated by responses to the El Niño Southern Oscillation. The trend toward earlier spawning was correlated with changes in sea surface temperature (SST) and mesozooplankton displacement volume, but not coastal upwelling. SST and upwelling were correlated with delays in fish phenology. For species with 20th century advances in phenology, future projections indicate that current trends will continue unabated. The fate of species with delayed phenology is less clear due to differences between Intergovernmental Panel on Climate Change models in projected upwelling trends. PMID:26159416

Natural ocean acidification at Papagayo upwelling system (north Pacific Costa Rica): implications for reef development

NASA Astrophysics Data System (ADS)

Sánchez-Noguera, Celeste; Stuhldreier, Ines; Cortés, Jorge; Jiménez, Carlos; Morales, Álvaro; Wild, Christian; Rixen, Tim

2018-04-01

Numerous experiments have shown that ocean acidification impedes coral calcification, but knowledge about in situ reef ecosystem response to ocean acidification is still scarce. Bahía Culebra, situated at the northern Pacific coast of Costa Rica, is a location naturally exposed to acidic conditions due to the Papagayo seasonal upwelling. We measured pH and pCO2 in situ during two non-upwelling seasons (June 2012, May-June 2013), with a high temporal resolution of every 15 and 30 min, respectively, using two Submersible Autonomous Moored Instruments (SAMI-pH, SAMI-CO2). These results were compared with published data from the 2009 upwelling season. Findings revealed that the carbonate system in Bahía Culebra shows a high temporal variability. Incoming offshore waters drive intra- and interseasonal changes. Lowest pH (7.8) and highest pCO2 (658.3 µatm) values measured during a cold-water intrusion event in the non-upwelling season were similar to those minimum values reported from upwelling season (pH = 7.8, pCO2 = 643.5 µatm), unveiling that natural acidification also occurs sporadically in the non-upwelling season. This affects the interaction of photosynthesis, respiration, calcification and carbonate dissolution and the resulting diel cycle of pH and pCO2 in the reefs of Bahía Culebra. During the non-upwelling season, the aragonite saturation state (Ωa) rises to values of > 3.3 and during the upwelling season falls below 2.5. The Ωa threshold values for coral growth were derived from the correlation between measured Ωa and coral linear extension rates which were obtained from the literature and suggest that future ocean acidification will threaten the continued growth of reefs in Bahía Culebra. These data contribute to building a better understanding of the carbonate system dynamics and coral reefs' key response (e.g., coral growth) to natural low-pH conditions, in upwelling areas in the eastern tropical Pacific and beyond.

Wind-driven changes of surface current, temperature, and chlorophyll observed by satellites north of New Guinea

NASA Astrophysics Data System (ADS)

Radenac, Marie-Hélène; Léger, Fabien; Messié, Monique; Dutrieux, Pierre; Menkes, Christophe; Eldin, Gérard

2016-04-01

Satellite observations of wind, sea level and derived currents, sea surface temperature (SST), and chlorophyll are used to expand our understanding of the physical and biological variability of the ocean surface north of New Guinea. Based on scarce cruise and mooring data, previous studies differentiated a trade wind situation (austral winter) when the New Guinea Coastal Current (NGCC) flows northwestward and a northwest monsoon situation (austral summer) when a coastal upwelling develops and the NGCC reverses. This circulation pattern is confirmed by satellite observations, except in Vitiaz Strait where the surface northwestward flow persists. We find that intraseasonal and seasonal time scale variations explain most of the variance north of New Guinea. SST and chlorophyll variabilities are mainly driven by two processes: penetration of Solomon Sea waters and coastal upwelling. In the trade wind situation, the NGCC transports cold Solomon Sea waters through Vitiaz Strait in a narrow vein hugging the coast. Coastal upwelling is generated in westerly wind situations (westerly wind event, northwest monsoon). Highly productive coastal waters are advected toward the equator and, during some westerly wind events, toward the eastern part of the warm pool. During El Niño, coastal upwelling events and northward penetration of Solomon Sea waters combine to influence SST and chlorophyll anomalies.

Evaluation of Water Residence Time, Submarine Groundwater Discharge, and Maximum New Production Supported by Groundwater Borne Nutrients in a Coastal Upwelling Shelf System

NASA Astrophysics Data System (ADS)

Luo, Xin; Jiao, Jiu Jimmy; Liu, Yi; Zhang, Xiaolang; Liang, Wenzhao; Tang, Danling

2018-01-01

The biogeochemical processes in the continental shelf systems are usually extensively influenced by coastal upwelling and submarine groundwater discharge (SGD). Using eastern Hainan upwelling shelf system as an example, this study fully investigates SGD and coastal upwelling and their effects on the coastal nutrient loadings to the mixing layer of eastern Hainan shelf. Based on the spatial distributions of 223Ra and 228Ra, water residence time is estimated to be 16.9 ± 8.9 days. Based on the mass balance models of 226Ra and 228Ra, the total SGD of the eastern Hainan shelf is estimated to be 0.8 × 108 and 1.4 × 108 m3 d-1, respectively. The groundwater borne dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphate (DIP) are estimated to be up to 1121.8 and 20.4 μM m2 d-1. The coastal upwelling delivers 2741.8 μM m2 d-1 DIN and 217.7 μM m2 d-1 DIP into the mixing layer, which are predominant in all the exogenous nutrient inputs. The groundwater borne DIN will support a maximum new production of 7.5 mM C m2 d-1, about up to 24.0% of the total new production in the study area. SGD-derived nutrient could be significant as a missing DIN to support the new production in the mixing layer of eastern Hainan shelf. The findings contribute to a better understanding of biogeochemical processes under the influences of SGD and coastal upwelling in the study area and other similar coastal upwelling systems.

Cetacean distributions relative to ocean processes in the northern California Current System

NASA Astrophysics Data System (ADS)

Tynan, Cynthia T.; Ainley, David G.; Barth, John A.; Cowles, Timothy J.; Pierce, Stephen D.; Spear, Larry B.

2005-01-01

Associations between cetacean distributions, oceanographic features, and bioacoustic backscatter were examined during two process cruises in the northern California Current System (CCS) during late spring and summer 2000. Line-transect surveys of cetaceans were conducted across the shelf and slope, out to 150 km offshore from Newport, Oregon (44.6°N) to Crescent City, California (41.9°N), in conjunction with multidisciplinary mesoscale and fine-scale surveys of ocean and ecosystem structure. Occurrence patterns (presence/absence) of cetaceans were compared with hydrographic and ecological variables (e.g., sea surface salinity, sea surface temperature, thermocline depth, halocline depth, chlorophyll maximum, distance to the center of the equatorward jet, distance to the shoreward edge of the upwelling front, and acoustic backscatter at 38, 120, 200 and 420 kHz) derived from a towed, undulating array and a bioacoustic system. Using a multiple logistic regression model, 60.2% and 94.4% of the variation in occurrence patterns of humpback whales Megaptera novaeangliae during late spring and summer, respectively, were explained. Sea surface temperature, depth, and distance to the alongshore upwelling front were the most important environmental variables during June, when humpbacks occurred over the slope (200-2000 m). During August, when humpbacks concentrated over a submarine bank (Heceta Bank) and off Cape Blanco, sea surface salinity was the most important variable, followed by latitude and depth. Humpbacks did not occur in the lowest salinity water of the Columbia River plume. For harbor porpoise Phocoena phocoena, the model explained 79.2% and 70.1% of the variation in their occurrence patterns during June and August, respectively. During spring, latitude, sea surface salinity, and thermocline gradient were the most important predictors. During summer, latitude and distance to the inshore edge of the upwelling front were the most important variables. Typically a coastal species, harbor porpoises extended their distribution farther offshore at Heceta Bank and at Cape Blanco, where they were associated with the higher chlorophyll concentrations in these regions. Pacific white-sided dolphin Lagenorhynchus obliquidens was the most numerous small cetacean in early June, but was rare during August. The model explained 44.5% of the variation in their occurrence pattern, which was best described by distance to the upwelling front and acoustic backscatter at 38 kHz. The model of the occurrence pattern of Dall's porpoise Phocoenoides dalli was more successful when mesoscale variability in the CCS was higher during summer. Thus, the responses of cetaceans to biophysical features and upwelling processes in the northern CCS were both seasonally and spatially specific. Heceta Bank and associated flow-topography interactions were very important to a cascade of trophic dynamics that ultimately influenced the distribution of foraging cetaceans. The higher productivity associated with upwelling near Cape Blanco also had a strong influence on the distribution of cetaceans.

Mussel farming impact on pelagic production and respiration rates in a coastal upwelling embayment (Ría de Vigo, NW Spain)

NASA Astrophysics Data System (ADS)

Froján, María; Castro, Carmen G.; Zúñiga, Diana; Arbones, Belén; Alonso-Pérez, Fernando; Figueiras, Francisco G.

2018-05-01

This paper provides the first diagnosis of the impact of mussel farming on the primary production (PP) and the metabolic balance in a coastal upwelling region (Ría de Vigo). Measurements of size-fractionated PP and microbial plankton metabolism were performed outside (reference station; ReS) and inside the farming area (raft station; RaS). At ReS, integrated PP was higher during upwelling (1.05 ± 0.45 g C m-2 d-1) with microphytoplankton dominating carbon fixation (74 ± 14%). The significance of nanophytoplankton and picophytoplankton increased during winter linked to lower PP (0.24 ± 0.03 g C m-2 d-1). Water column at ReS was always autotrophic with net community production (NCP) ranging from 186 ± 67 mmol O2 m-2 d-1 during upwelling to 43 ± 22 mmol O2 m-2 d-1 in winter. At RaS, there was a decrease in PP attributable not only to mussel consumption but also to the lower irradiance under mussel rafts. Concomitant decrease in NCP was also observed (by 56%), yet remained autotrophic, supporting the view that under current conditions food does not limit mussel growth in the Ría, thus securing the carrying capacity of the system in terms of production.

Sedimentary silicon isotope indicates the Kuroshio subsurface upwelling in the East China Sea

NASA Astrophysics Data System (ADS)

Zhao, Y.; Yang, S.; Su, N.

2017-12-01

The Kuroshio as the western boundary current of the North Pacific subtropical circulation, originates from east of the Philippine Islands, and flows northeastward along the eastern coast of Taiwan. It's subsurface water intrudes the East China Sea (ECS) and forms a typical upwelling on the inner shelf, which may play an important role in the material and heat transport, biogeochemical process and marine ecosystem of the ECS.To date, most previous studies on the Kuroshio subsurface upwelling focuse on the seasonal and interannual variations, and few researches touch on the upwelling evolution in the geologic past. In this study, eight short sediment cores were taken along the ECS inner shelf (upwelling area), which allow us to reconstruct the upwelling history over the last several hundred years. Although conventional indexes of oceanographic changes, such as salinity, temperature and hydrogen and oxygen isotope, provide valuable constraints on the modern oceanic circulation and water mass movements, how to reconstruct them from geologic records is always a challenging work. In this contribution, we present the data of stable silicon isotope, biogenic opal, diatom assemblages, element geochemistry and stable carbon and nitrogen isotopes of these core sediments, and aim to decipher the Kuroshio subsurface upwelling history on the ECS shelf. We will also illustrate the difference in δ30Si signals between small (<30 um) and large (>150 um) diatom fractions, and test whether it is an effective indicator for paleo-upwelling intensity.

Eddy properties in the Southern California Current System

NASA Astrophysics Data System (ADS)

Chenillat, Fanny; Franks, Peter J. S.; Capet, Xavier; Rivière, Pascal; Grima, Nicolas; Blanke, Bruno; Combes, Vincent

2018-05-01

The California Current System (CCS) is an eastern boundary upwelling system characterized by strong eddies that are often generated at the coast. These eddies contribute to intense, long-distance cross-shelf transport of upwelled water with enhanced biological activity. However, the mechanisms of formation of such coastal eddies, and more importantly their capacity to trap and transport tracers, are poorly understood. Their unpredictability and strong dynamics leave us with an incomplete picture of the physical and biological processes at work, their effects on coastal export, lateral water exchange among eddies and their surrounding waters, and how long and how far these eddies remain coherent structures. Focusing our analysis on the southern part of the CCS, we find a predominance of cyclonic eddies, with a 25-km radius and a SSH amplitude of 6 cm. They are formed near shore and travel slightly northwest offshore for 190 days at 2 km day-1. We then study one particular, representative cyclonic eddy using a combined Lagrangian and Eulerian numerical approach to characterize its kinematics. Formed near shore, this eddy trapped a core made up of 67% California Current waters and 33% California Undercurrent waters. This core was surrounded by other waters while the eddy detached from the coast, leaving the oldest waters at the eddy's core and the younger waters toward the edge. The eddy traveled several months as a coherent structure, with only limited lateral exchange within the eddy.

Development and Utilization of the Regional Oceanic Modeling System (ROMS)

DTIC Science & Technology

2008-09-30

the Peru/ Chile Current system (PCS). Emphasis is put on the PCS due to its direct connection with the equatorial region; this makes it a good...nearshore wind drop-off that occurs in reality. Numerical simulations of the Peru/ Chile (PCS) and the California (CCS) upwelling systems are being... Chile and the USWC 4. More subtle effects of the wind/SST coupling on the mesoscale eddy activity are now investigated. RESULTS Since funds for

Water masses and mesoscale control on latitudinal and cross-shelf variations in larval fish assemblages off NW Africa

NASA Astrophysics Data System (ADS)

Olivar, M. Pilar; Sabatés, Ana; Pastor, Maria V.; Pelegrí, Josep L.

2016-11-01

We explore the associations between larval fish assemblages and oceanographic conditions in the upper ocean (top 200 m) along the African slope, from tropical (15°N) to subtropical (35°N) latitudes, during a period of intense upwelling. In this extensive region, the northward Mauritanian Current and Poleward Undercurrent carry South Atlantic Central Waters (SACW) while the southward Canary Upwelling Current transports North Atlantic Central Waters (NACW). South of Cape Blanc we only find SACW, and north of Cape Blanc there is NACW far offshore and a combination of NACW and SACW nearshore, separated by the Canary Upwelling Front (CUF). The larvae of different myctophid species serve as indicators of the water masses, e.g. S. veranyi and M. punctatum were found in some coastal stations that were dominated by NACW, while the tropical mesopelagic B. argyrogaster, H. macrochir, M. affine and S. kreffti were associated to the SACW. The along-slope offshore convergence of NACW and SACW takes place at the Cape Verde Frontal Zone (CVFZ), representing a region of extensive offshore export for larvae of coastal species, S. pilchardus and E. encrasicolus, far from their nearshore spawning area. The large-scale frontal systems (CVFZ and CUF) and mesoscale eddies contribute to retain larvae within productive waters, influencing both coastal and oceanic species.

Summary of the physical oceanography of the Pacific Northwest Coast

DOE Office of Scientific and Technical Information (OSTI.GOV)

Purdy, D.F.

The technical report summarizes current information on the physical oceanography of the Pacific Coast of Washington and Oregon, including information on currents, water mass characteristics, vertical stratification and mixing, upwelling, and waves. A general outline of the California current system is given, including the California and Davidson surface currents, the California and Washington undercurrents, and shelf currents. Conditions affecting local and nearshore currents, considered important in the event of an oil spill, are discussed. A summary of wave data is included from several sources including the Corps of Engineers WIS (Wave Information Study), based on meteorological information, and the Mineralsmore » Management Service's Coastal Wave Statistical Data Base (CWSDB), based on high quality data from a system of buoys.« less

Spatiotemporal variation of vertical particle fluxes and modelled chlorophyll a standing stocks in the Benguela Upwelling System

NASA Astrophysics Data System (ADS)

Vorrath, Maria-Elena; Lahajnar, Niko; Fischer, Gerhard; Libuku, Viktor Miti; Schmidt, Martin; Emeis, Kay-Christian

2018-04-01

Marine particle fluxes from high productive coastal upwelling systems return upwelled CO2 and nutrients to the deep ocean and sediments and have a substantial impact on the global carbon cycle. This study examines relations between production regimes on the shelf and over the continental margin of the Benguela Upwelling System (BUS) in the SE Atlantic Ocean. Data of composition and timing of vertical particle flux come from sediment trap time series (deployed intermittently between 1988 and 2014) in the regions Walvis Ridge, Walvis Bay, Luederitz and Orange River. We compare their seasonal variability to modelled patterns of chlorophyll concentrations in a 3-D ecosystem model. Both modelled seasonal chlorophyll a standing stocks and sampled particle flux patterns are highly correspondent with a bimodal seasonal cycle offshore the BUS. The material in the particle flux in offshore traps is dominantly carbonate (40-70%), and flux peaks in offshore particle flux originate from two independent events: in austral autumn thermocline shoaling and vertical mixing are decoupled from coastal upwelling, while fluxes in spring coincide with the upwelling season, indicated by slightly elevated biogenic opal values at some locations. Coastal particle fluxes are characterized by a trimodal pattern and are dominated by biogenic opal (22-35%) and organic matter (30-60%). The distinct seasonality in observed fluxes on the shelf is caused by high variability in production, sinking behaviour, wind stress, and hydrodynamic processes. We speculate that global warming will increase ocean stratification and alter coastal upwelling, so that consequences for primary production and particle flux in the BUS are inevitable.

N2O production by nitrifier denitrification in the Benguela Upwelling System

NASA Astrophysics Data System (ADS)

Frame, C. H.; Hou, L.; Lehmann, M. F.

2014-12-01

The Benguela upwelling system off the coast of southwestern Africa is an important zone of marine N2O production whose upwelling rates vary seasonally. Here we present N2O stable isotopic and isotopomeric data collected during a period of high upwelling (September 2013) and low upwelling (January 2014). During both periods, 15N-nitrite and 15N-ammonium tracer inucbation experiments were used to investigate N2O production by ammonia oxidizing microorganisms in the top 150m of the water column. N2O production from 15N-ammonium was not measurable during these incubations. However, we detected N2O production from 15N-nitrite, suggesting that nitrifier denitrification is a source of shallow N2O in this region. Furthermore, decreasing the pH of the incubation water enhanced the amount of N2O produced, suggesting that upwelling of CO2-rich/low-pH deep water may enhance N2O production in this region. Finally, we present our incubation data in the larger context of the N2O and nitrite isotopic and concentration profiles, with an eye toward comparing incubation-based N2O production rates with profile-based estimates.

Temporal and spatial variability of dissolved organic and inorganic phosphorus, and metrics of phosphorus bioavailability in an upwelling-dominated coastal system

NASA Astrophysics Data System (ADS)

Ruttenberg, Kathleen C.; Dyhrman, Sonya T.

2005-10-01

High-frequency temporal and spatial shifts in the various dissolved P pools (total, inorganic, and organic) are linked to upwelling/relaxation events and to phytoplankton bloom dynamics in the upwelling-dominated Oregon coastal system. The presence and regulation of alkaline phosphatase activity (APA) is apparent in the bulk phytoplankton population and in studies of cell-specific APA using Enzyme Labeled Fluorescence (ELF®). Spatial and temporal variability are also evident in phytoplankton community composition and in APA. The spatial pattern of dissolved phosphorus and APA variability can be explained by bottom-controlled patterns of upwelling, and flushing times of different regions within the study area. The presence of APA in eukaryotic taxa indicates that dissolved organic phosphorus (DOP) may contribute to phytoplankton P nutrition in this system, highlighting the need for a more complete understanding of P cycling and bioavailability in the coastal ocean.

Modeling of the mesoscale structure of coupled upwelling/downwelling events and the related input of nutrients to the upper mixed layer in the Gulf of Finland, Baltic Sea

NASA Astrophysics Data System (ADS)

Zhurbas, Victor; Laanemets, Jaan; Vahtera, Emil

2008-05-01

A high resolution numerical study is undertaken to simulate an upwelling event along the northern coast of the Gulf of Finland, 21-29 July 1999, which was documented well by in situ and remote measurements. The simulated sequence of SST maps shows a reasonably good resemblance to that of satellite infrared imagery, including both mesoscale coherent structures (filaments or squirts) and the whole process of post-upwelling relaxation of the temperature field. Upwelling along the northern coast of the Gulf is accompanied by downwelling along the southern coast so that two longshore baroclinic jets and related fronts are developed simultaneously. When the strong westerly winds producing the upwelling/downwelling weaken, the longshore jets become unstable and produce transverse jets, cold/warm water squirts. Using pseudo-random simulated fields of temperature and velocity of currents, the apparent lateral diffusivity due to squirts is directly estimated at 500 m2 s-1. The model is also applied to estimate nutrient transport. Simulated phosphate concentration in the surface layer at the cold side of upwelling front is found to be about 0.3 mmol m-3 which is consistent with observations. The total content of phosphorus and nitrogen in the upper 10 m layer of the Gulf introduced by the upwelling event is estimated to be 387 and 36 tons, respectively. It follows, that the upwelling event transports nutrients into the upper layer with clear excess of phosphorus (N:P = 36:387 = 0.093) compared to the Redfield ratio of 7.2. Therefore phosphorus input caused by upwelling during summer most likely promotes nitrogen-fixing cyanobacteria blooms.

Potential and timescales for oxygen depletion in coastal upwelling systems: A box-model analysis

NASA Astrophysics Data System (ADS)

Harrison, C. S.; Hales, B.; Siedlecki, S.; Samelson, R. M.

2016-05-01

A simple box model is used to examine oxygen depletion in an idealized ocean-margin upwelling system. Near-bottom oxygen depletion is controlled by a competition between flushing with oxygenated offshore source waters and respiration of particulate organic matter produced near the surface and retained near the bottom. Upwelling-supplied nutrients are consumed in the surface box, and some surface particles sink to the bottom where they respire, consuming oxygen. Steady states characterize the potential for hypoxic near-bottom oxygen depletion; this potential is greatest for faster sinking rates, and largely independent of production timescales except in that faster production allows faster sinking. Timescales for oxygen depletion depend on upwelling and productivity differently, however, as oxygen depletion can only be reached in meaningfully short times when productivity is rapid. Hypoxia thus requires fast production, to capture upwelled nutrients, and fast sinking, to deliver the respiration potential to model bottom waters. Combining timescales allows generalizations about tendencies toward hypoxia. If timescales of sinking are comparable to or smaller than the sum of those for respiration and flushing, the steady state will generally be hypoxic, and results indicate optimal timescales and conditions exist to generate hypoxia. For example, the timescale for approach to hypoxia lengthens with stronger upwelling, since surface particle and nutrient are shunted off-shelf, in turn reducing subsurface respiration and oxygen depletion. This suggests that if upwelling winds intensify with climate change the increased forcing could offer mitigation of coastal hypoxia, even as the oxygen levels in upwelled source waters decline.

Wind modulation of upwelling at the shelf-break front off Patagonia: Observational evidence

NASA Astrophysics Data System (ADS)

Carranza, M. M.; Gille, S. T.; Piola, A. R.; Charo, M.; Romero, S. I.

2017-03-01

The South-Atlantic Patagonian shelf is the largest chlorophyll-a (Chl-a) hot spot in Southern Ocean color images. While a persistent 1500 km long band of high Chl-a along the shelf-break front (SBF) is indicative of upwelling, the mechanisms that drive it are not entirely known. Along-front wind oscillations can enhance upwelling and provide a nutrient pumping mechanism at shelf-break fronts of western boundary currents. Here we assess wind-induced upwelling at the SBF off Patagonia from daily satellite Chl-a and winds, historical hydrographic observations, cross-shelf Chl-a fluorescence transects from two cruises, and in situ winds and water column structure from a mooring site. Satellite Chl-a composites segregated by along-front wind direction indicate that surface Chl-a is enhanced at the SBF with southerly winds and suppressed with northerly winds. Northerly winds also result in enhanced Chl-a further offshore (˜25-50 km). Synoptic transects as well as mean hydrographic sections segregated by along-front winds show isopycnals tilted upward for southerly winds. Spring observations from the mooring also suggest that southerly winds destratify the water column and northerly winds restratify, in agreement with Ekman transport interacting with the front. Moreover, changes in water column temperature lag along-front wind forcing by 2-4 days. Our results suggest that oscillations in along-front winds, on timescales typical of atmospheric storms (2-10 days), can significantly modulate the upwelling and Chl-a concentrations at the SBF off Patagonia, revealing the importance of wind-induced upwelling for shelf-slope exchange at shelf-break fronts of western boundary currents.

Oxygen cycling in the northern Benguela Upwelling System: Modelling oxygen sources and sinks

NASA Astrophysics Data System (ADS)

Schmidt, Martin; Eggert, Anja

2016-12-01

This paper elucidates the oxygen dynamics in the northern Benguela Upwelling System by means of process oriented, numerical modelling. Owing to the complex physical-biological interaction in this system, a coupled hydrodynamic-biogeochemical model is required to grasp the various aspects of the oxygen dynamics. We used high-resolution atmospheric fields derived from observations to force our model, available since 1999. The model results represent a 15 years, consistent data set of realistic hydrographic and ecosystem variables, including oxygen distribution patterns. After a concise description of the main aspects of the model, we use the model data to analyse the components contributing to the oxygen dynamics, namely, the ocean circulation, the exchange between ocean and atmosphere as well as the local biogeochemical oxygen cycling in the system. We thoroughly validate the model with available field observations and remote sensing data. The strengths of coastal upwelling, which controls the nutrient supply to the euphotic zone, as well as the poleward undercurrent that carries oxygen and nutrients to the shelf in the northern Benguela Upwelling System are well reproduced in the model. Among the biological oxygen sinks, mineralisation in the sediment, respiration of zooplankton and nitrification in the water column are important. We also found that vertical migration of zooplankton in response to the oxygen conditions provides a regulating feedback, which may prevent a complete deoxygenation of suboxic waters. As long as oxygen or nitrate are available in the bottom waters, the activities of chemolithoautotrophic sulphur bacteria on the sediment surface keep the redoxcline within the sediment and prevent the release of hydrogen sulphide into the water column. By horizontal integration of the simulated ocean-atmosphere oxygen flux, it can be shown that the Kunene upwelling cell between 16 ° S and 18 ° S is a boundary between the equatorial ocean, characterise by weak oxygen release to the atmosphere, and the subtropical Benguela Upwelling System governed by an enhanced and seasonal varying flux. Furthermore, a comparison of oxygen fluxes controlled by physical transport versus biogeochemical processes shows that the physical processes dominate in the northern Benguela Upwelling System.

Upwelling regime off the Cabo Frio region in Brazil and impact on acoustic propagation.

PubMed

Calado, Leandro; Camargo Rodríguez, Orlando; Codato, Gabriel; Contrera Xavier, Fabio

2018-03-01

This work introduces a description of the complex upwelling regime off the Cabo Frio region in Brazil and shows that ocean modeling, based on the feature-oriented regional modeling system (FORMS) technique, can produce reliable predictions of sound speed fields for the corresponding shallow water environment. This work also shows, through the development of simulations, that the upwelling regime can be responsible for the creation of shadow coastal zones, in which the detection probability is too low for an acoustic source to be detected. The development of the FORMS technique and its validation with real data, for the particular region of coastal upwelling off Cabo Frio, reveals the possibility of a sustainable and reliable forecast system for the corresponding (variable in space and time) underwater acoustic environment.

Radiolarian Indices of Paleoproductivity Variation in the late Pleistocene Benguela Upwelling System, ODP Site 1084

NASA Astrophysics Data System (ADS)

Bittniok, B. B.; Lazarus, D. B.; Diester-Haass, L.; Billups, K.; Meyers, P.

2006-12-01

Changes in export productivity play a significant role in ocean carbon budgets and global climate change. Proxies for export productivity can be difficult to interpret: benthic foraminifera accumulation rates (BFAR) can be affected by carbonate dissolution in organic-carbon rich sediments; bulk opal can be affected by silica limitation of source waters. Recent work (Lazarus et al. 2006; Mar. Micropal.) has shown that a new index based on radiolarian faunal changes (WADE ratio) correlates well to total organic carbon (TOC) values from the same samples over the long term (latest Miocene-Recent) history of productivity in the Benguela Upwelling System (BUS). We present new data on variation in export productivity proxies (WADE, TOC, carbonate, radiolarian opal, BFAR) for the last glacial-interglacial cycle from ODP Site 1084, located just offshore from the main coastal upwelling cells of the BUS. Our age model, from mean Quaternary sedimentation rates (Leg 175 Scientific Results), is in accordance with cyclic variation in other climate sensitive parameters (carbonate and color reflectance). Although opal content and radiolarian preservation is only moderate in our samples, WADE values vary significantly and suggest higher productivity during the last glacial, in accordance with current interpretations of BUS history. Radiolarian opal accumulation is also higher during the last glacial, suggesting that silica limitation (opal paradox) conditions did not dominate over this time period. Similar results for bulk opal have been reported from late Quaternary piston cores from the more northerly Congo upwelling region (Schneider et al, 1997; Paleoc.). We conclude that WADE ratios are a useful proxy for late Pleistocene productivity in the BUS at glacial- interglacial time scales.

Seasonality of coastal upwelling trends under future warming scenarios along the southern limit of the canary upwelling system

NASA Astrophysics Data System (ADS)

Sousa, Magda Catarina; Alvarez, Ines; deCastro, Maite; Gomez-Gesteira, Moncho; Dias, João Miguel

2017-04-01

The Canary Upwelling Ecosystem (CUE) is one of the four most important upwelling sites around the world in terms of primary production, with coastal upwelling mostly a year-round phenomenon south of 30°N. Based on annual future projections, several previous studies indicated that global warming will intensify coastal upwelling in the northern region and will induce its weakening at the southernmost latitudes. However, analysis of historical data, showed that coastal upwelling depends on the length of the time series, the season, and even the database used. Thus, despite previous efforts, an overall detailed description of seasonal upwelling trends and their effects on sea surface temperature (SST) along the Canary coast over the 21st century remains unclear. To address this issue, several regional and global wind and SST climate models from CORDEX and CMIP5 projects for the period 1976-2099 were analyzed. This research provides new insights about coastal upwelling trends under future warming scenarios for the CUE, with results showing opposite patterns for upwelling index (UI) trends depending on the season. A weakening of the UI occurs from May to August all along the coast, whereas it increases from October to April. Analysis of SST trends reveals a general warming throughout the area, although the warming rate is considerably lower near the shore than at open ocean locations due to coastal upwelling effects. In addition, SST projections show higher warming rates from May to August than from October to April in response to the future decreasing trend in the UI during the summer months.

Summertime sea surface temperature fronts associated with upwelling around the Taiwan Bank

NASA Astrophysics Data System (ADS)

Lan, Kuo-Wei; Kawamura, Hiroshi; Lee, Ming-An; Chang, Yi; Chan, Jui-Wen; Liao, Cheng-Hsin

2009-04-01

It is well known that upwelling of subsurface water is dominant around the Taiwan Bank (TB) and the Penghu (PH) Islands in the southern Taiwan Strait in summertime. Sea surface temperature (SST) frontal features and related phenomena around the TB upwelling and the PH upwelling were investigated using long-term AVHRR (1996-2005) and SeaWiFS (1998-2005) data received at the station of National Taiwan Ocean University. SST and chlorophyll-a (Chl-a) images with a spatial resolution of 0.01° were generated and used for the monthly SST and Chl-a maps. SST fronts were extracted from each SST images and gradient magnitudes (GMs); the orientations were derived for the SST fronts. Monthly maps of cold fronts where the cooler SSTs were over a shallower bottom were produced from the orientation. Areas with high GMs (0.1-0.2 °C/km) with characteristic shapes appeared at geographically fixed positions around the TB/PH upwelling region where SSTs were lower than the surrounding waters. The well-shaped high GMs corresponded to cold fronts. Two areas with high Chl-a were found around the TB and PH Islands. The southern border of the high-Chl-a area in the TB upwelling area was outlined by the high-GM area. Shipboard measurements of snapshot vertical sections of temperature (T) and salinity (S) along the PH Channel showed a dome structure east of PH Islands, over which low SST and high GM in the maps of the corresponding month were present. Clear evidence of upwelling (vertically uniform distributions of T and S) was indicated at the TB edge in the T and S sections close to TB upwelling. This case of upwelling may be caused by bottom currents ascending the TB slope as pointed out by previous studies. The position of low SSTs in the monthly maps matched the upwelling area, and the high GMs corresponded to the area of eastern surface fronts in the T/S sections.

Controlling factors of the seasonal variability of productivity in the southern Humboldt Current System (30-40°S): A biophysical modeling approach

NASA Astrophysics Data System (ADS)

Vergara, Odette A.; Echevín, Vincent; Sepúlveda, Héctor Hito; Quiñones, Renato A.

2017-09-01

The spatial and seasonal variability of nutrients and chlorophyll in the southern Humboldt Current System were assessed using a high-resolution regional ocean circulation model (ROMS) coupled to a biogeochemical model (Pelagic-Interactions Scheme for carbon and Ecosystem Studies; PISCES). The simulated nutrients and chlorophyll fields were validated using satellite and in situ observations at a continental shelf time-series station. The annual cycles of modeled chlorophyll and nutrients were consistent with the highest values observed in spring and summer, which is in agreement with enhanced upwelling observations. Co-limitation of phytoplankton growth by nutrients and light was analyzed for diatoms, the dominant phytoplankton group in the simulations. The results showed that co-limitation, near the coast, was governed in autumn and winter by light, and by silicate in spring and summer, whereas other nutrients were limiting offshore between January and April. Nutrient transport in the surface layer was analyzed. Vertical advection reflected areas with higher coastal upwelling, and was partly offset by horizontal processes related to eddy-induced transport from the nearshore to the open ocean. Vertical mixing was shown to play a key role in replenishing the surface layer with nutrients.

Life in the sea of plenty: Seasonal and regional comparison of physiological performance of Euphausia hanseni in the northern Benguela upwelling system

NASA Astrophysics Data System (ADS)

Werner, Thorsten; Buchholz, Cornelia; Buchholz, Friedrich

2015-09-01

Variability in upwelling events may lead to periods of constrained food availability in the northern Benguela upwelling system (NBUS), thereby affecting the physiological state and metabolic activity of euphausiids. Most attention has so far been paid to seasonal effects but little is known about regional variability. Metabolic activity (expressed by respiration and excretion rates) and physiological state (expressed by reproductive effort and moult activity) in Euphausia hanseni were examined at different stations during austral summer (minimum upwelling) and austral winter (maximum upwelling). Overall, regional differences in physiological state, influencing metabolic activity, were greater than seasonal ones, indicating favourable conditions for growth and reproduction year-round. Higher respiration rates were found for females in more advanced stages of sexual development. Moult stage did not affect oxygen consumption rates, however. The physiological state of E. hanseni at the time of capture may serve as a meaningful indicator of the associated hydrographic conditions in the NBUS, to be further used in eco-system analysis on seasonal or long-term time scales. A latitudinal comparison of species highlights the extraordinary physiological plasticity of euphausiids.

Sub-regional ecosystem variability in the Canary Current upwelling

NASA Astrophysics Data System (ADS)

Arístegui, Javier; Barton, Eric D.; Álvarez-Salgado, Xosé A.; Santos, A. Miguel P.; Figueiras, Francisco G.; Kifani, Souad; Hernández-León, Santiago; Mason, Evan; Machú, Eric; Demarcq, Hervé

2009-12-01

The Canary Current upwelling ecosystem (CanC) constitutes one of the four main eastern boundary upwelling ecosystems (EBUEs) of the world, thus hosting high productivity and fisheries. Recent observations indicate that the CanC region as a whole has been experiencing a progressive warming and a decrease in productivity over the last decades. This overall trend is however not directly reflected in the fisheries of the region. Here we update recent results and previous reviews on the CanC, covering aspects from the physical environment to fish populations and fisheries on a range of time scales. We approach these topics, when possible, through a comparative exploration of the biogeographical characteristics of different sub-regions comprising this ecosystem. This review shows that variability in coastline configuration, shelf width, coastal upwelling, nutrient fertilization, productivity, or retentive vs. dispersive physical mechanisms, among other factors, may help explain sub-regional differences in fish distributions and abundances in the CanC. Nevertheless, the lack of systematic information on the regional variability of physical and biological processes hampers an integrated understanding of the relative contribution of natural vs. human-induced variability in the populations of at least small-pelagic fishes and their associated fisheries.

Application of LANDSAT satellite imagery and oceanographic data for verification of an upwelling mathematical model. [Atlantic Coast of Brazil

NASA Technical Reports Server (NTRS)

Dejesusparada, N. (Principal Investigator); Tanaka, K.; Almeida, E. G.

1978-01-01

The author has identified the following significant results. Data obtained during the cruise of the Cabo Frio and from LANDSAT imagery are used to discuss the characteristics of a linear model which simulates wind induced currents calculated from meteorological conditions at the time of the mission. There is a significant correspondance between the model of simulated horizontal water circulation, sea surface temperature, and surface currents observed on LANDSAT imagery. Close approximations were also observed between the simulation of vertical water movement (upwelling) and the oceanographic measurements taken along a series of points of the prevailing currents.

Modeling coastal upwelling around a small-scale coastline promontory

NASA Astrophysics Data System (ADS)

Haas, K. A.; Cai, D.; Freismuth, T. M.; MacMahan, J.; Di Lorenzo, E.; Suanda, S. H.; Kumar, N.; Miller, A. J.; Edwards, C. A.

2016-12-01

On the US west coast, northerly winds drive coastal ocean upwelling, an important process which brings cold nutrient rich water to the nearshore. The coastline geometry has been shown to be a significant factor in the strength of the upwelling process. In particular, the upwelling in the lee of major headlands have been shown to be enhanced. Recent observations from the Pt. Sal region on the coast of southern California have shown the presence of cooler water south of a small (350 m) rocky promontory (Mussel Pt.) during upwelling events. The hypothesis is that the small scale promontory is creating a lee side enhancement to the upwelling. To shed some light on this process, numerical simulations of the inner shelf region centered about Pt. Sal are conducted with the ROMS module of the COAWST model system. The model system is configured with four nested grids with resolutions ranging from approximately 600 m to the outer shelf ( 200 m) to the inner shelf ( 66 m) and finally to the surf zone ( 22 m). A solution from a 1 km grid encompassing our domain provides the boundary conditions for the 600 m grid. Barotropic tidal forcing is incorporated at the 600 m grid to provide tidal variability. This model system with realistic topography and bathymetry, winds and tides, is able to isolate the forcing mechanisms that explain the emergence of the cold water mass. The simulations focus on the time period of June - July, 2015 corresponding to the pilot study in which observational experiment data was collected. The experiment data in part consists of in situ measurement, which includes mooring with conductivity, temperature, depth, and flow velocity. The model simulations are able to reproduce the important flow features including the cooler water mass south of Mussel Pt. As hypothesized, the strength of the upwelling is enhanced on the side of Mussel Pt. In addition, periods of wind relaxation where the upwelling ceases and even begins to transform towards downwelling is analyzed.

High Resolution Upwelling Cycles in Guaymas and Cariaco Basins over the late Holocene: Coupling Between the Western Atlantic and Eastern Pacific?

NASA Astrophysics Data System (ADS)

Goni, M. A.

2005-12-01

The recent past history of sea surface temperature (SST) conditions in two wind-dominated upwelling systems, Guaymas Basin (Gulf of California) and Cariaco Basin (Venezuela) was investigated using the alkenone-based UK'37 index. Both of these systems undergo marked seasonal SST changes of 4-10 degrees C, which are associated with wind-driven upwelling and thermal stratification cycles. Both Guaymas and Cariaco Basins are also characterized by suboxic to anoxic bottom waters that result in undisturbed, varved sediments. Confirmation that the seasonal SST trends are accurately incorporated into the UK'37 ratios of sinking particles was achieved using sediment trap samples. Analyses of sediment cores from Guaymas and Cariaco Basins yielded high-resolution (decadal) records of SST conditions in the overlying water column from 1700 to 2000 AD. The trends in the UK'37 index revealed general increases in the SST at both sites over that last 300 years associated with the end of the little ice age. However, in addition to this long-term trend, higher-frequency (~ 50 years) changes in SST that ranged from 1-3 degrees C were observed. We speculate that these decadal trends in SST reflect variations in the intensity of wind-driven upwelling at these sites. Most interestingly, there is a marked contrast in the timing of the SST values between Guaymas and Cariaco so that periods of enhanced upwelling in Guyamas Basin are characterized by decreased upwelling in Cariaco Basin (and vice versa). We propose that these contrasting records reflect differences in the response of wind-driven upwelling to changes in the position of the Intertropical Convergence Zone over the western Atlantic and the subtropical High over the eastern Pacific. The connection between these two upwelling systems and its significance for paleoreconstruction studies will be explored further.

First studies of bottom boundary currents in the Ría de Vigo (NW Iberian upwelling system)

NASA Astrophysics Data System (ADS)

Villacieros-Robineau, N.; Herrera, J. H.; Castro, C. G.; Piedracoba, S.; Rosón, G.

2012-04-01

The NW Iberian Upwelling system has a set of physical and chemical characteristics that determine the ecology at the coast, specifically inside the Rías Baixas where activities like raft culture have a significant weight in the local economy. Although several studies have dealt with the physical processes driving the rías general circulation, no previous research has faced the study of bottom boundary currents. This work studies the behavior of bottom currents inside the Rías Baixas and identifies their possible forcing mechanism. For tackling this issue, high resolution time series of bottom currents by means of a downwards looking ADCP (3-5 meters above the bottom) were recorded at one site in the Ría de Vigo covering the four seasons of the climate year 2004 - 2005. Our analysis shows that most of the time (aprox. 70 -80%), the bottom currents respond to a logarithmic profile being possible to apply the law of the wall. This pattern can be applied to the residual component and also to the tidal component of the currents. Based on this logarithmic fit, we have obtained characteristic parameters like shear stress and shear velocity. Our results point to a coupling among shear stress, shelf winds and runoff. Other important conclusion is the relative importance of tidal shear stress versus residual shear stress because the typical assumption of tidal has more influence is not true always. In some occasions when there are neap tides and high shelf winds the residual stress could be just three times the tidal ones.

Macro-Scale Patterns in Upwelling/Downwelling Activity at North American West Coast

PubMed Central

Saldívar-Lucio, Romeo; Di Lorenzo, Emanuele; Nakamura, Miguel; Villalobos, Héctor; Lluch-Cota, Daniel; Del Monte-Luna, Pablo

2016-01-01

The seasonal and interannual variability of vertical transport (upwelling/downwelling) has been relatively well studied, mainly for the California Current System, including low-frequency changes and latitudinal heterogeneity. The aim of this work was to identify potentially predictable patterns in upwelling/downwelling activity along the North American west coast and discuss their plausible mechanisms. To this purpose we applied the min/max Autocorrelation Factor technique and time series analysis. We found that spatial co-variation of seawater vertical movements present three dominant low-frequency signals in the range of 33, 19 and 11 years, resembling periodicities of: atmospheric circulation, nodal moon tides and solar activity. Those periodicities might be related to the variability of vertical transport through their influence on dominant wind patterns, the position/intensity of pressure centers and the strength of atmospheric circulation cells (wind stress). The low-frequency signals identified in upwelling/downwelling are coherent with temporal patterns previously reported at the study region: sea surface temperature along the Pacific coast of North America, catch fluctuations of anchovy Engraulis mordax and sardine Sardinops sagax, the Pacific Decadal Oscillation, changes in abundance and distribution of salmon populations, and variations in the position and intensity of the Aleutian low. Since the vertical transport is an oceanographic process with strong biological relevance, the recognition of their spatio-temporal patterns might allow for some reasonable forecasting capacity, potentially useful for marine resources management of the region. PMID:27893826

Mass-specific respiration of mesozooplankton and its role in the maintenance of an oxygen-deficient ecological barrier (BEDOX) in the upwelling zone off Chile upon presence of a shallow oxygen minimum zone

NASA Astrophysics Data System (ADS)

Donoso, Katty; Escribano, Ruben

2014-01-01

A shallow oxygen minimum zone (OMZ) in the coastal upwelling zone off Chile may vertically confine most zooplankton to a narrow (< 50 m) upper layer. From laboratory experiments, we estimated oxygen consumption of the mesozooplankton community obtained in Bay of Mejillones, northern Chile (23°S) in May 2010, December 2010 and August 2011. Mass-specific respiration rates were in the range of 8.2-24.5 μmol O2 mg dry mass- 1 day- 1, at an average temperature of 12 °C. Estimates of the mesozooplankton biomass in the water column indicated that its aerobic respiration may remove daily a maximum of about 20% of oxygen available at the base of the oxycline. Since previous work indicates that zooplankton aggregate near the base of the oxycline, the impact of aerobic respiration on oxygen content might be even stronger at this depth. Mesozooplankton respiration, along with community respiration by microorganisms near the base of the oxycline and a strongly stratified condition (limiting vertical flux of O2), are suggested as being critical factors causing and maintaining a persistent subsurface oxygen-deficient ecological barrier (BEDOX) in the upwelling zone. This BEDOX layer can have a major role in affecting and regulating zooplankton distribution and their dynamics in the highly productive coastal upwelling zone of the Humboldt Current System.

Transformation of Deep Water Masses Along Lagrangian Upwelling Pathways in the Southern Ocean

NASA Astrophysics Data System (ADS)

Tamsitt, V.; Abernathey, R. P.; Mazloff, M. R.; Wang, J.; Talley, L. D.

2018-03-01

Upwelling of northern deep waters in the Southern Ocean is fundamentally important for the closure of the global meridional overturning circulation and delivers carbon and nutrient-rich deep waters to the sea surface. We quantify water mass transformation along upwelling pathways originating in the Atlantic, Indian, and Pacific and ending at the surface of the Southern Ocean using Lagrangian trajectories in an eddy-permitting ocean state estimate. Recent related work shows that upwelling in the interior below about 400 m depth is localized at hot spots associated with major topographic features in the path of the Antarctic Circumpolar Current, while upwelling through the surface layer is more broadly distributed. In the ocean interior upwelling is largely isopycnal; Atlantic and to a lesser extent Indian Deep Waters cool and freshen while Pacific deep waters are more stable, leading to a homogenization of water mass properties. As upwelling water approaches the mixed layer, there is net strong transformation toward lighter densities due to mixing of freshwater, but there is a divergence in the density distribution as Upper Circumpolar Deep Water tends become lighter and dense Lower Circumpolar Deep Water tends to become denser. The spatial distribution of transformation shows more rapid transformation at eddy hot spots associated with major topography where density gradients are enhanced; however, the majority of cumulative density change along trajectories is achieved by background mixing. We compare the Lagrangian analysis to diagnosed Eulerian water mass transformation to attribute the mechanisms leading to the observed transformation.

Secondary contact and asymmetrical gene flow in a cosmopolitan marine fish across the Benguela upwelling zone

PubMed Central

Reid, K; Hoareau, T B; Graves, J E; Potts, W M; dos Santos, S M R; Klopper, A W; Bloomer, P

2016-01-01

The combination of oceanographic barriers and habitat heterogeneity are known to reduce connectivity and leave specific genetic signatures in the demographic history of marine species. However, barriers to gene flow in the marine environment are almost never impermeable which inevitably allows secondary contact to occur. In this study, eight sampling sites (five along the South African coastline, one each in Angola, Senegal and Portugal) were chosen to examine the population genetic structure and phylogeographic history of the cosmopolitan bluefish (Pomatomus saltatrix), distributed across a large South-east Atlantic upwelling zone. Molecular analyses were applied to mtDNA cytochrome b, intron AM2B1 and 15 microsatellite loci. We detected uncharacteristically high genetic differentiation (FST 0.15–0.20; P<0.001) between the fish sampled from South Africa and the other sites, strongly influenced by five outlier microsatellite loci located in conserved intergenic regions. In addition, differentiation among the remaining East Atlantic sites was detected, although mtDNA indicated past isolation with subsequent secondary contact between these East Atlantic populations. We further identified secondary contact, with unidirectional gene flow from South Africa to Angola. The directional contact is likely explained by a combination of the northward flowing offshore current and endogenous incompatibilities restricting integration of certain regions of the genome and limiting gene flow to the south. The results confirm that the dynamic system associated with the Benguela current upwelling zone influences species distributions and population processes in the South-east Atlantic. PMID:27436525

Secondary contact and asymmetrical gene flow in a cosmopolitan marine fish across the Benguela upwelling zone.

PubMed

Reid, K; Hoareau, T B; Graves, J E; Potts, W M; Dos Santos, S M R; Klopper, A W; Bloomer, P

2016-11-01

The combination of oceanographic barriers and habitat heterogeneity are known to reduce connectivity and leave specific genetic signatures in the demographic history of marine species. However, barriers to gene flow in the marine environment are almost never impermeable which inevitably allows secondary contact to occur. In this study, eight sampling sites (five along the South African coastline, one each in Angola, Senegal and Portugal) were chosen to examine the population genetic structure and phylogeographic history of the cosmopolitan bluefish (Pomatomus saltatrix), distributed across a large South-east Atlantic upwelling zone. Molecular analyses were applied to mtDNA cytochrome b, intron AM2B1 and 15 microsatellite loci. We detected uncharacteristically high genetic differentiation (F ST 0.15-0.20; P<0.001) between the fish sampled from South Africa and the other sites, strongly influenced by five outlier microsatellite loci located in conserved intergenic regions. In addition, differentiation among the remaining East Atlantic sites was detected, although mtDNA indicated past isolation with subsequent secondary contact between these East Atlantic populations. We further identified secondary contact, with unidirectional gene flow from South Africa to Angola. The directional contact is likely explained by a combination of the northward flowing offshore current and endogenous incompatibilities restricting integration of certain regions of the genome and limiting gene flow to the south. The results confirm that the dynamic system associated with the Benguela current upwelling zone influences species distributions and population processes in the South-east Atlantic.

Anomalous Upwelling in Nan Wan: July 2008

DTIC Science & Technology

2009-12-01

Head Ruth H. Preller 7300 Security, Code 1226 Office of Couns sl.Code 1008.3 ADOR/Director NCST E. R. Franchi , 7000 Public Affairs (Unclassified...State University (OSU) tidal forcing drives the tidal currents. A global weather forecast model (Navy Operational Global Atmospheric Prediction...system derives its open ocean boundary conditions from NRL global NCOM (Navy Co- astal Ocean Model) (Rhodes et al. 2002) that operates daily

The OMZ and nutrient features as a signature of interannual and low-frequency variability in the Peruvian upwelling system

NASA Astrophysics Data System (ADS)

Graco, Michelle I.; Purca, Sara; Dewitte, Boris; Castro, Carmen G.; Morón, Octavio; Ledesma, Jesús; Flores, Georgina; Gutiérrez, Dimitri

2017-10-01

Over the last decades, the Humboldt Current upwelling ecosystem, particularly the northern component off the coast of Peru, has drawn the interest of the scientific community because of its unique characteristics: it is the upwelling system with the biggest catch productivity despite the fact it is embedded in a shallow and intense oxygen minimum zone (OMZ). It is also an area of intense nitrogen loss and anammox activity and experiences large interannual variability associated with the equatorial remote forcing. In this context, we examined the oceanographic and biogeochemical variability associated with the OMZ off central Peru from a monthly time series (1996-2011) recorded off the coast of Callao (12° 02' S, 77° 29' W). The data reveal a rich spectrum of variability in the OMZ that includes frequencies ranging from seasonal to interannual scales. Due to the efficient oceanic teleconnection off Peru, the observed variability is interpreted in the light of an estimate of the equatorial Kelvin wave contribution to sea level anomalies considering the peculiarities of its vertical structure (i.e., the first two baroclinic modes). The span of the data set allows us to contrast two OMZ regimes. The strong regime is associated with the strong 1997-1998 equatorial Pacific El Niño, during which the OMZ adjusted to Kelvin-wave-induced downwelling conditions that switched off the upwelling and drastically reduced nutrient availability. The weak regime corresponds to the post-2000 period associated with the occurrence of moderate central Pacific El Niño events and enhanced equatorial Kelvin wave activity, in which mean upwelling conditions are maintained. It is shown that the characteristics of the coupling between physics and biogeochemistry is distinct between the two regimes with the weak regime being associated with a larger explained variance in biogeochemical properties not linearly related to the ENSO oceanic teleconnection. The data also reveal a long-term trend from 1999 corresponding to a deepening of the oxygen-deficient waters and warming. The implications of our results for understanding the OMZ dynamics off Peru are discussed.

Evaluation of the saturation state of Aragonite, at Baja California Coast, Mexico

NASA Astrophysics Data System (ADS)

Oliva, N. L.; Hernandez, J. M.; Camacho, V.; Deldagillo, F.; Torres, V.; Siqueiros-Valencia, A.; Castro, R.

2012-12-01

The carbonate ion is in excess in the surface waters of the world's ocean, and is necessary for the formation of carbonate structures such as oyster shells and echinoderm skeletons. Seasonal upwelling in the California Current system brings dense water with high partial pressure of carbon dioxide to the sea surface and into contact with the atmosphere in the near shore. In order to evaluate the saturation state of Aragonite (ΩA), from November 2009 to November 2011, biweekly monitoring of dissolved inorganic carbon (CID), total alkalinity (TA), temperature (T) and salinity (S), in the intertidal zone at "Arbolitos" was conducted. During the same period, a mooring buoy located 3 km from Arbolitos recorded data every 3 hours for T and carbon dioxide partial pressure (pCO2), at the sea and in the air 1 meter above the sea surface.The ΩA was calculated for both study sites where upwelling events occurred during the spring-summer months. The data at both Arbolitos and mooring buoy shows that during the upwelling season maximum DIC concentration (2150μmol kg -1) and maximum pCO2 (863 μatm) correspond to the lowest temperature (11°C) and ΩA values (1; equilibrium). During the ten upwelling events identified (T < 15 °C, pCO2 > 387 μatm), the ΩA values (3 to 1) were not lower than the saturation limit (value of 1).The results show that the calcifying organisms in this region are persisting in an environment with variable ΩA conditions. It was determined that the longer the duration of the upwelling event, the lower the ΩA value, and the higher the change in pCO2. The ΩA interval (approximately 3 to 1) is not the same from year to year. This suggests interannual variations in upwelling, possibly due to El Niño (present during the first six months of 2010), and La Niña conditions (from July 2010 to November 2011).; t; Characteristics of the ten events of upwelling, at arbolitos and at the moorign buoy. For both study sites it shows the duration, pCO2, ΩA y pH values.

Production regimes in four eastern boundary current systems

NASA Technical Reports Server (NTRS)

Carr, M. E.; Kearns, E. J.

2003-01-01

High productivity (maxima 3 g C m(sup -2)day(sup -1)) of the Eastern Boundary Currents (EBCs), i.e. the California, Peru-Humboldt, Canary and Benguela Currents, is driven by a combination of local forcing and large-scale circulation. The characteristics of the deep water brought to the surface by upwelling favorable winds depend on the large-scale circulation patterns. Here we use a new hydrographic and nutrient climatology together with satellite measurements ofthe wind vector, sea-surface temperature (SST), chlorophyll concentration, and primary production modeled from ocean color to quantify the meridional and seasonal patterns of upwelling dynamics and biological response. The unprecedented combination of data sets allows us to describe objectively the variability for small regions within each current and to characterize the governing factors for biological production. The temporal and spatial environmental variability was due in most regions to large-scale circulation, alone or in combination with offshore transport (local forcing). The observed meridional and seasonal patterns of biomass and primary production were most highlycorrelated to components representing large-scale circulation. The biomass sustained by a given nutrient concentration in the Atlantic EBCs was twice as large as that of the Pacific EBCs. This apparent greater efficiency may be due toavailability of iron, physical retention, or differences in planktonic community structure.

Coastal Upwelling Drives Intertidal Assemblage Structure and Trophic Ecology.

PubMed

Reddin, Carl J; Docmac, Felipe; O'Connor, Nessa E; Bothwell, John H; Harrod, Chris

2015-01-01

Similar environmental driving forces can produce similarity among geographically distant ecosystems. Coastal oceanic upwelling, for example, has been associated with elevated biomass and abundance patterns of certain functional groups, e.g., corticated macroalgae. In the upwelling system of Northern Chile, we examined measures of intertidal macrobenthic composition, structure and trophic ecology across eighteen shores varying in their proximity to two coastal upwelling centres, in a hierarchical sampling design (spatial scales of >1 and >10 km). The influence of coastal upwelling on intertidal communities was confirmed by the stable isotope values (δ13C and δ15N) of consumers, including a dominant suspension feeder, grazers, and their putative resources of POM, epilithic biofilm, and macroalgae. We highlight the utility of muscle δ15N from the suspension feeding mussel, Perumytilus purpuratus, as a proxy for upwelling, supported by satellite data and previous studies. Where possible, we used corrections for broader-scale trends, spatial autocorrelation, ontogenetic dietary shifts and spatial baseline isotopic variation prior to analysis. Our results showed macroalgal assemblage composition, and benthic consumer assemblage structure, varied significantly with the intertidal influence of coastal upwelling, especially contrasting bays and coastal headlands. Coastal topography also separated differences in consumer resource use. This suggested that coastal upwelling, itself driven by coastline topography, influences intertidal communities by advecting nearshore phytoplankton populations offshore and cooling coastal water temperatures. We recommend the isotopic values of benthic organisms, specifically long-lived suspension feeders, as in situ alternatives to offshore measurements of upwelling influence.

Coastal Upwelling Drives Intertidal Assemblage Structure and Trophic Ecology

PubMed Central

Reddin, Carl J.; Docmac, Felipe; O’Connor, Nessa E.; Bothwell, John H.; Harrod, Chris

2015-01-01

Similar environmental driving forces can produce similarity among geographically distant ecosystems. Coastal oceanic upwelling, for example, has been associated with elevated biomass and abundance patterns of certain functional groups, e.g., corticated macroalgae. In the upwelling system of Northern Chile, we examined measures of intertidal macrobenthic composition, structure and trophic ecology across eighteen shores varying in their proximity to two coastal upwelling centres, in a hierarchical sampling design (spatial scales of >1 and >10 km). The influence of coastal upwelling on intertidal communities was confirmed by the stable isotope values (δ13C and δ15N) of consumers, including a dominant suspension feeder, grazers, and their putative resources of POM, epilithic biofilm, and macroalgae. We highlight the utility of muscle δ15N from the suspension feeding mussel, Perumytilus purpuratus, as a proxy for upwelling, supported by satellite data and previous studies. Where possible, we used corrections for broader-scale trends, spatial autocorrelation, ontogenetic dietary shifts and spatial baseline isotopic variation prior to analysis. Our results showed macroalgal assemblage composition, and benthic consumer assemblage structure, varied significantly with the intertidal influence of coastal upwelling, especially contrasting bays and coastal headlands. Coastal topography also separated differences in consumer resource use. This suggested that coastal upwelling, itself driven by coastline topography, influences intertidal communities by advecting nearshore phytoplankton populations offshore and cooling coastal water temperatures. We recommend the isotopic values of benthic organisms, specifically long-lived suspension feeders, as in situ alternatives to offshore measurements of upwelling influence. PMID:26214806

Differences in coastal and oceanic SST trends north of Yucatan Peninsula

NASA Astrophysics Data System (ADS)

Varela, R.; Costoya, X.; Enriquez, C.; Santos, F.; Gómez-Gesteira, M.

2018-06-01

The coastal area north of Yucatan has experienced a cooling SST trend from 1982 to 2015 during the upwelling season (May-September) that contrasts with the warming observed at the adjacent ocean area. Different drivers were analyzed to identify the possible causes of that unusual coastal cooling. Changes in coastal upwelling and in sea-atmosphere heat fluxes are not consistent with the observed coastal cooling. The eastward shift of the Yucatan Current observed over the last decades is hypothesized as the most probable cause of coastal cooling. This shift enhances the vertical transport of cold deeper water to the continental shelf from where it is pumped to the surface by upwelling favorable westerly winds.

On the presence of coastal upwelling along the northeastern Tyrrhenian coast

NASA Astrophysics Data System (ADS)

Martellucci, Riccardo; Melchiorri, Cristiano; Costanzo, Lorenzo; Marcelli, Marco

2017-04-01

The Mediterranean region shows a high climate variability due to the interactions between mid-latitude and tropical processes. This variability makes the Mediterranean a potentially vulnerable region to climatic changes. The present research aims to investigate the hydrographical response to Northerly wind in the northeastern Tyrrhenian coast, to identify the relations between upwelling events and teleconnection patterns. In the Tyrrhenian basin northerly winds flow between North-East and North-West and could be considered upwelling favorable winds. This atmospheric circulation can causes a divergent flow near the coast that generates a subsurface water flows inshore toward the coast up to the surface layer that is upwelling. This phenomenon strongly influence the marine ecosystems, contributing to the supply of nutrients and affecting the primary producers. In this context multi-platform observing system is an important tool to follow the evolution of these phenomena. Sea temperature and wind field acquired by the C-CEMS Observing system were used to identify upwelling phenomena between 2012 and 2016, in the coastal area of Civitavecchia, Northern Tyrrhenian sea, Italy. Moreover a thirty years' wind-driven upwelling conditions have been studied in the area. ERA-Interim (ECMWF) wind data for the period 1982-2012 have been used to compute the distribution of upwelling favorable wind events. These have been compared to "Copernicus Marine Environment Monitoring Service" Sea Surface Temperature (SST) to compute upwelling events. Upwelling favorable wind has been defined in the sector between Northwest and Northeast (Wd >330°N & Wd < 30°N). Wind speed has been divided into three classes: between 4 m/s and 6 m/s, between 6 m/s and 8 m/s and greater than 8 m/s. Sea Surface Temperature have been analyzed to define SST field for wind-driven coastal upwelling assessment. SST minima along the coast was used to identify upwelling from satellite imagery. The two datasets were compared and only the days that presented those characteristics were chosen. ERA-Interim (ECMWF) sea level pressure data over the Europe for the period 1982 -2012 have been used to compute the most relevant teleconnection patterns through Empirical Orthogonal Function's analysis. An increase of upwelling events in the Tyrrhenian coast is observed in the last thirty years; the occurrence of upwelling events has a seasonal oscillation, with a maximum frequency during winter and spring seasons. In the last decade an increase of these events in winter and a decrease in spring is observed; also a recurrence of these events in summer season has been identified, without the specific contribution of one of atmospheric regimes. Data analyzed shows a decrement in Atlantic Ridge (AR) regime and an increment in West Blocking (WBL) regime, especially for the event characterized by wind speeds greater than 8m/s.

Nutrient controls on new production in the Bodega Bay, California, coastal upwelling plume

NASA Astrophysics Data System (ADS)

Dugdale, R. C.; Wilkerson, F. P.; Hogue, V. E.; Marchi, A.

2006-12-01

A theoretical framework for the time-dependent processes leading to the high rates of new production in eastern boundary upwelling systems has been assembled from a series of past upwelling studies. As part of the CoOP WEST (Wind Events and Shelf Transport) study, new production in the Bodega Bay upwelling area and it's control by ambient nitrate and ammonium concentrations and the advective wind regime are described. Data and analyses are focused primarily on the WEST 2001 cruise (May-June 2001) when the two legs differed greatly in wind regimes but not nutrient concentrations. Elevated concentrations of ammonium in upwelled water with high nitrate were observed in both legs. Nitrate uptake by phytoplankton as a function of nitrate concentration was linear rather than Michaelis-Menten-like, modulated by inhibitory levels of ammonium, yielding coefficients that enable the specific nitrate uptake element of new production to be estimated from nutrient concentrations. The range of specific nitrate uptake rates for the two legs of WEST 2001 were similar, essentially a physiological response to nutrient conditions. However, the low "realization" of new production i.e. incorporation of biomass as particulate nitrogen that occurred in this system compared to the theoretical maximum possible was determined by the strong advective and turbulent conditions that dominated the second leg of the WEST 2001 study. These data are compared with other upwelling areas using a physiological shift-up model [Dugdale, R.C., Wilkerson, F.P., Morel, A. 1990. Realization of new production in coastal upwelling areas: a means to compare relative performance. Limnology and Oceanography 35, 822-829].

Trace Element Geochemistry as a Tool for the Reconstruction of Upwelling Patterns at 12oS off Peru since the Last Glacial Maximum (LGM)

NASA Astrophysics Data System (ADS)

Boening, P.; Brumsack, H.; Wolf, A.

2002-05-01

Laminated sediments (core 106KL), recovered during R/V Sonne cruise 147 from the Peruvian upper slope mud lens at 12oS, were analyzed for bulk parameters (TOC, TIC, TS) and opal as well as major and trace element composition by XRF and ICP-MS in 5 cm intervals. The composition of the terrigenous-detrital sediment fraction is comparable to average shale. The sediments exhibit slight increases in biogenic silica (diatoms) and carbonate contents (foraminifera) in varying layers. The experimentally determined opal contents correlate well with Si/Al ratios. High TOC and P contents are due to enhanced primary productivity, high sedimentation rates and corresponding organic matter preservation under a strong OMZ. We distinguish between three different groups of elements: 1.) trace elements involved in bio-cycling (e.g. Cd, Ag, Ni, Cu) are highly enriched in the sediments due to their association with plankton, high sedimentation rates (preventing remobilization from the sediments) and fixation as sulfides. 2.) redox-sensitive elements (e.g. Re, Mo) are significantly enriched probably due to reduction and precipitation under suboxic/anoxic conditions. Diffusion of these elements from the water column into sub/anoxic sediments seems to be the controlling factor, besides sulfide precipitation. An average Re/Mo ratio of 1.3 indicates anoxic sedimentary conditions. Most trace elements correlate well with the TOC content presumably documenting productivity events. 3.) Al, Zr and Y are well correlated, presumably representing sporadic high-energy fluvial input from the continent or enhanced current velocities. The three element groups were used to reconstruct the upwelling patterns off Lima since the LGM: TOC content and Al-normalized trace element patterns from the bio/redox-sensitive fractions represent the signal from the water column, whereas Al, Y and Zr reflect the terrigenous input. During the LGM (about 17 ky BP) the site was hardly affected by upwelling as the upwelling cell was located more basinward. As the sea level rose during the Late Glacial (17-10 ky BP) the upwelling cell shifted towards the coast. The Early Holocene (10-5 ky BP) is not documented likely because strong currents (presumably the Peru counter current) eroded the slope. In the Late Holocene the upwelling cell was established at the site. However, a higher terrrigenous proportion and lower input from the water column suggest a basinward shifting of the upwelling cell during the Second Neoglacial (2000-2700 BP). Stronger Element/Al and TOC variabilities indicate the influence of El Nino during the Late Holocene.

Variability of Phytoplankton Size Structure in Response to Changes in Coastal Upwelling Intensity in the Southwestern East Sea

NASA Astrophysics Data System (ADS)

Shin, Jung-Wook; Park, Jinku; Choi, Jang-Geun; Jo, Young-Heon; Kang, Jae Joong; Joo, HuiTae; Lee, Sang Heon

2017-12-01

The aim of this study was to examine the size structure of phytoplankton under varying coastal upwelling intensities and to determine the resulting primary productivity in the southwestern East Sea. Samples of phytoplankton assemblages were collected on five occasions from the Hupo Bank, off the east coast of Korea, during 2012-2013. Because two major surface currents have a large effect on water mass transport in this region, we first performed a Backward Particle Tracking Experiment (BPTE) to determine the coastal sea from which the collected samples originated according to advection time of BPTE particles, following which we used upwelling age (UA) to determine the intensity of coastal upwelling in the region of origin for each sample. Only samples that were affected by coastal upwelling in the region of origin were included in subsequent analyses. We found that as UA increased, there was a decreasing trend in the concentration of picophytoplankton, and increasing trends in the concentration of nanophytoplankton and microphytoplankton. We also examined the relationship between the size structure of phytoplankton and primary productivity in the Ulleung Basin (UB), which has experienced significant variation over the past decade. We found that primary productivity in UB was closely related to the strength of the southerly wind, which is the most important mechanism for coastal upwelling in the southwestern East Sea. Thus, the size structure of phytoplankton is determined by the intensity of coastal upwelling, which is regulated by the southerly wind, and makes an important contribution to primary productivity.

Nonlocal impacts of the Loop Current on cross-slope near-bottom flow in the northeastern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Nguyen, Thanh-Tam; Morey, Steven L.; Dukhovskoy, Dmitry S.; Chassignet, Eric P.

2015-04-01

Cross-slope near-bottom motions near De Soto Canyon in the northeastern Gulf of Mexico are analyzed from a multidecadal ocean model simulation to characterize upwelling and downwelling, important mechanisms for exchange between the deep ocean and shelf in the vicinity of the 2010 BP Macondo well oil spill. Across the continental slope, large-scale depression and offshore movement of isopycnals (downwelling) occur more frequently when the Loop Current impinges upon the West Florida Shelf slope farther south. Upwelling and onshore movement of isopycnals occurs with roughly the same likelihood regardless of Loop Current impingement on the slope. The remote influence of Loop Current on the De Soto Canyon region downwelling is a consequence of a high-pressure anomaly that extends along the continental slope emanating from the location of Loop Current impact.

A dynamic box model of bioactive elements in the southern Taiwan Strait

NASA Astrophysics Data System (ADS)

Hua-Sheng, Hong; Shao-Ling, Shang

1994-06-01

A dynamic box model was applied to study the characteristics of biogeochemical cycling of PO4-P, NO3-N, AOU, POC and PON in the southern Taiwan Strait region based on the field data of the “Minnan Taiwan Bank Fishing Ground Upwelling Ecosystem Study” during the period of Dec. 1987-Nov. 1988. According to the unique hydrological and topographical features of the region, six boxes and three layers were considered in the model. The variation rates and fluxes of elements induced by horizontal current, upwelling, by diffusion, sinking of particles and biogeochemical processes were estimated respectively. Results further confirmed that upwellings had important effects in this region. The nearshore upwelling areas had net input fluxes of nutrients brought by upwelling water, also had high depletion rates of nutrients and production rates of particulate organic matter and dissolved oxygen. The abnormal net production of nutrients in the middle layer, (10-30 m) indicated the important role of bacteria in this high production region. The phytoplankton POC contributed about 28% of the total POC. POC settling out from the euphotic zone was estimated to be 2×10-6 g/(m2·s) which was about 35% of the primary production.

Short-term alteration of biotic and abiotic components of the pelagic system in a shallow bay produced by a strong natural hypoxia event.

PubMed

Hernández-Miranda, Eduardo; Veas, Rodrigo; Anabalón, Valeria; Quiñones, Renato A

2017-01-01

In January 2008 there was an intensive and extensive upwelling event in the southern Humboldt Current System. This event produced an intrusion of water with low dissolved oxygen into Coliumo Bay, which caused massive mortality and the beaching of pelagic and benthic organisms, including zooplankton. During this event, which lasted 3 to 5 days, we studied and evaluated the effect of the hypoxic water in the bay on the abundance of macrozooplankton, nanoplankton and microphytoplankton, the concentration of several nutrients and hydrographic conditions. At the beginning of the hypoxia event the water column had very low dissolved oxygen concentrations (<0.5 mL O2 L-1), low temperatures and high salinity which are characteristics of the oxygen minimum zone from the Humboldt Current System. Redox, pH, nitrate, phosphate, silicate and chlorophyll-a values were the lowest, while nitrate and the phaeopigment values were the highest. The N:P ratio was below 16, and the abundance of nano- and microphytoplankton were at their lowest, the latter also with the lowest proportion of live organisms. Macrozooplankton had the greatest abundance during hypoxia, dominated mainly by crustacean, fish eggs and amphipods. The hypoxia event generated a strong short-term alteration of all biotic and abiotic components of the pelagic system in Coliumo Bay and the neighboring coastal zone. These negative effects associated with strong natural hypoxia events could have important consequences for the productivity and ecosystem functioning of the coastal zone of the Humboldt Current System if, as suggested by several models, winds favorable to upwelling should increase due to climate change. The effects of natural hypoxia in this coastal zone can be dramatic especially for pelagic and benthic species not adapted to endure conditions of low dissolved oxygen.

Radiation and speciation of pelagic organisms during periods of global warming: the case of the common minke whale, Balaenoptera acutorostrata.

PubMed

Pastene, Luis A; Goto, Mutsuo; Kanda, Naohisa; Zerbini, Alexandre N; Kerem, Dan; Watanabe, Kazuo; Bessho, Yoshitaka; Hasegawa, Masami; Nielsen, Rasmus; Larsen, Finn; Palsbøll, Per J

2007-04-01

How do populations of highly mobile species inhabiting open environments become reproductively isolated and evolve into new species? We test the hypothesis that elevated ocean-surface temperatures can facilitate allopatry among pelagic populations and thus promote speciation. Oceanographic modelling has shown that increasing surface temperatures cause localization and reduction of upwelling, leading to fragmentation of feeding areas critical to pelagic species. We test our hypothesis by genetic analyses of populations of two closely related baleen whales, the Antarctic minke whale (Balaenoptera bonaerensis) and common minke whale (Balaenoptera acutorostrata) whose current distributions and migration patterns extent are largely determined by areas of consistent upwelling with high primary production. Phylogeographic and population genetic analyses of mitochondrial DNA control-region nucleotide sequences collected from 467 whales sampled in four different ocean basins were employed to infer the evolutionary relationship among populations of B. acutorostrata by rooting an intraspecific phylogeny with a population of B. bonaerensis. Our findings suggest that the two species diverged in the Southern Hemisphere less than 5 million years ago (Ma). This estimate places the speciation event during a period of extended global warming in the Pliocene. We propose that elevated ocean temperatures in the period facilitated allopatric speciation by disrupting the continuous belt of upwelling maintained by the Antarctic Circumpolar Current. Our analyses revealed that the current populations of B. acutorostrata likely diverged after the Pliocene some 1.5 Ma when global temperatures had decreased and presumably coinciding with the re-establishment of the polar-equatorial temperature gradient that ultimately drives upwelling. In most population samples, we detected genetic signatures of exponential population expansions, consistent with the notion of increasing carrying capacity after the Pliocene. Our hypothesis that prolonged periods of global warming facilitate speciation in pelagic marine species that depend on upwelling should be tested by comparative analyses in other pelagic species.

The use of circulation weather types to predict upwelling activity along the Western Iberian Peninsula coast

NASA Astrophysics Data System (ADS)

Ramos, Alexandre M.; Cordeiro Pires, Ana; Sousa, Pedro M.; Trigo, Ricardo M.

2013-04-01

Coastal upwelling is a phenomenon that occurs in most western oceanic coasts due to the presence of mid-latitude high-pressure systems that generate equatorward winds along the coast and consequent offshore displacement of surface waters that in turn cause deeper, colder, nutrient-rich waters to arise. In western Iberian Peninsula (IP) the high-pressure system associated to northerly winds occurs mainly during spring and summer. Upwelling systems are economically relevant, being the most productive regions of the world ocean and crucial for fisheries. In this work, we evaluate the intra- and inter-annual variability of the Upwelling Index (UI) off the western coast of the IP considering four locations at various latitudes: Rias Baixas, Aveiro, Figueira da Foz and Cabo da Roca. In addition, the relationship between the variability of the occurrence of several circulation weather types (Ramos et al., 2011) and the UI variability along this coast was assessed in detail, allowing to discriminate which types are frequently associated with strong and weak upwelling activity. It is shown that upwelling activity is mostly driven by wind flow from the northern quadrant, for which the obtained correlation coefficients (for the N and NE types) are higher than 0.5 for the four considered test locations. Taking into account these significant relationships, we then developed statistical multi-linear regression models to hindcast upwelling series (April to September) at the four referred locations, using monthly frequencies of circulation weather types as predictors. Modelled monthly series reproduce quite accurately observational data, with correlation coefficients above 0.7 for all locations, and relatively small absolute errors. Ramos AM, Ramos R, Sousa P, Trigo RM, Janeira M, Prior V (2011) Cloud to ground lightning activity over Portugal and its association with Circulation Weather Types. Atmospheric Research 101:84-101. doi: 10.1016/j.atmosres.2011.01

Bacterial and Archaeal Communities Variability Associated with Upwelling and Anthropogenic Pressures in the Protection Area of Arraial do Cabo (Cabo Frio region - RJ).

PubMed

Coelho-Souza, Sergio A; Araújo, Fábio V; Cury, Juliano C; Jesus, Hugo E; Pereira, Gilberto C; Guimarães, Jean R D; Peixoto, Raquel S; Dávila, Alberto M R; Rosado, Alexandre S

2015-09-01

Upwelling systems contain a high diversity of pelagic microorganisms and their composition and activity are defined by factors like temperature and nutrient concentration. Denaturing gradient gel electrophoresis (DGGE) technique was used to verify the spatial and temporal genetic variability of Bacteria and Archaea in two stations of the Arraial do Cabo coastal region, one under upwelling pressure and another under anthropogenic pressure. In addition, biotic and abiotic variables were measured in surface and deep waters from three other stations between these stations. Six samplings were done during a year and adequately represented the degrees of upwelling and anthropogenic pressures to the system. Principal Component Analysis (PCA) showed negative correlations between the concentrations of ammonia and phosphorous with prokaryotic secondary production and the total heterotrophic bacteria. PCA also showed negative correlation between temperature and the abundance of prokaryotic cells. Bacterial and archaeal compositions were changeable as were the oceanographic conditions, and upwelling had a regional pressure while anthropogenic pressure was punctual. We suggest that the measurement of prokaryotic secondary production was associated with both Bacteria and Archaea activities, and that substrate availability and temperature determine nutrients cycling.

Interpretation of remotely sensed data and its applications in oceanography

NASA Technical Reports Server (NTRS)

Parada, N. D. J. (Principal Investigator); Tanaka, K.; Inostroza, H. M.; Verdesio, J. J.

1982-01-01

The methodology of interpretation of remote sensing data and its oceanographic applications are described. The elements of image interpretation for different types of sensors are discussed. The sensors utilized are the multispectral scanner of LANDSAT, and the thermal infrared of NOAA and geostationary satellites. Visual and automatic data interpretation in studies of pollution, the Brazil current system, and upwelling along the southeastern Brazilian coast are compared.

The Effect of Alongcoast Advection on Pacific Northwest Shelf and Slope Water Properties in Relation to Upwelling Variability

NASA Astrophysics Data System (ADS)

Stone, Hally B.; Banas, Neil S.; MacCready, Parker

2018-01-01

The Northern California Current System experiences highly variable seasonal upwelling in addition to larger basin-scale variability, both of which can significantly affect its water chemistry. Salinity and temperature fields from a 7 year ROMS hindcast model of this region (43°N-50°N), along with extensive particle tracking, were used to study interannual variability in water properties over both the upper slope and the midshelf bottom. Variation in slope water properties was an order of magnitude smaller than on the shelf. Furthermore, the primary relationship between temperature and salinity anomalies in midshelf bottom water consisted of variation in density (cold/salty versus warm/fresh), nearly orthogonal to the anomalies along density levels (cold/fresh versus warm/salty) observed on the upper slope. These midshelf anomalies were well-explained (R2 = 0.6) by the combination of interannual variability in local and remote alongshore wind stress, and depth of the California Undercurrent (CUC) core. Lagrangian analysis of upper slope and midshelf bottom water shows that both are affected simultaneously by large-scale alongcoast advection of water through the northern and southern boundaries. The amplitude of anomalies in bottom oxygen and dissolved inorganic carbon (DIC) on the shelf associated with upwelling variability are larger than those associated with typical variation in alongcoast advection, and are comparable to observed anomalies in this region. However, a large northern intrusion event in 2004 illustrates that particular, large-scale alongcoast advection anomalies can be just as effective as upwelling variability in changing shelf water properties on the interannual scale.

The Effect of Alongcoast Advection on Pacific Northwest Shelf and Slope Water Properties in Relation to Upwelling Variability

PubMed Central

Banas, Neil S.; MacCready, Parker

2018-01-01

Abstract The Northern California Current System experiences highly variable seasonal upwelling in addition to larger basin‐scale variability, both of which can significantly affect its water chemistry. Salinity and temperature fields from a 7 year ROMS hindcast model of this region (43°N–50°N), along with extensive particle tracking, were used to study interannual variability in water properties over both the upper slope and the midshelf bottom. Variation in slope water properties was an order of magnitude smaller than on the shelf. Furthermore, the primary relationship between temperature and salinity anomalies in midshelf bottom water consisted of variation in density (cold/salty versus warm/fresh), nearly orthogonal to the anomalies along density levels (cold/fresh versus warm/salty) observed on the upper slope. These midshelf anomalies were well‐explained (R 2 = 0.6) by the combination of interannual variability in local and remote alongshore wind stress, and depth of the California Undercurrent (CUC) core. Lagrangian analysis of upper slope and midshelf bottom water shows that both are affected simultaneously by large‐scale alongcoast advection of water through the northern and southern boundaries. The amplitude of anomalies in bottom oxygen and dissolved inorganic carbon (DIC) on the shelf associated with upwelling variability are larger than those associated with typical variation in alongcoast advection, and are comparable to observed anomalies in this region. However, a large northern intrusion event in 2004 illustrates that particular, large‐scale alongcoast advection anomalies can be just as effective as upwelling variability in changing shelf water properties on the interannual scale. PMID:29938149

Differential Distributions of Synechococcus Subgroups Across the California Current System

PubMed Central

Paerl, Ryan W.; Johnson, Kenneth S.; Welsh, Rory M.; Worden, Alexandra Z.; Chavez, Francisco P.; Zehr, Jonathan P.

2011-01-01

Synechococcus is an abundant marine cyanobacterial genus composed of different populations that vary physiologically. Synechococcus narB gene sequences (encoding for nitrate reductase in cyanobacteria) obtained previously from isolates and the environment (e.g., North Pacific Gyre Station ALOHA, Hawaii or Monterey Bay, CA, USA) were used to develop quantitative PCR (qPCR) assays. These qPCR assays were used to quantify populations from specific narB phylogenetic clades across the California Current System (CCS), a region composed of dynamic zones between a coastal-upwelling zone and the oligotrophic Pacific Ocean. Targeted populations (narB subgroups) had different biogeographic patterns across the CCS, which appear to be driven by environmental conditions. Subgroups C_C1, D_C1, and D_C2 were abundant in coastal-upwelling to coastal-transition zone waters with relatively high to intermediate ammonium, nitrate, and chl. a concentrations. Subgroups A_C1 and F_C1 were most abundant in coastal-transition zone waters with intermediate nutrient concentrations. E_O1 and G_O1 were most abundant at different depths of oligotrophic open-ocean waters (either in the upper mixed layer or just below). E_O1, A_C1, and F_C1 distributions differed from other narB subgroups and likely possess unique ecologies enabling them to be most abundant in waters between coastal and open-ocean waters. Different CCS zones possessed distinct Synechococcus communities. Core California current water possessed low numbers of narB subgroups relative to counted Synechococcus cells, and coastal-transition waters contained high abundances of Synechococcus cells and total number of narB subgroups. The presented biogeographic data provides insight on the distributions and ecologies of Synechococcus present in an eastern boundary current system. PMID:21833315

What drives the spatial variability of primary productivity and matter fluxes in the north-west African upwelling system? A modelling approach

NASA Astrophysics Data System (ADS)

Auger, Pierre-Amaël; Gorgues, Thomas; Machu, Eric; Aumont, Olivier; Brehmer, Patrice

2016-11-01

A comparative box analysis based on a multi-decadal physical-biogeochemical hindcast simulation (1980-2009) was conducted to characterize the drivers of the spatial distribution of phytoplankton biomass and production in the north-west (NW) African upwelling system. Alongshore geostrophic flow related to large-scale circulation patterns associated with the influence of coastal topography is suggested to modulate the coastal divergence, and then the response of nutrient upwelling to wind forcing. In our simulation, this translates into a coastal upwelling of nitrate being significant in all regions but the Cape Blanc (CB) area. However, upwelling is found to be the dominant supplier of nitrate only in the northern Saharan Bank (NSB) and the Senegalo-Mauritanian (SM) regions. Elsewhere, nitrate supply is dominated by meridional advection, especially off Cape Blanc. Phytoplankton displays a similar behaviour with a supply by lateral advection which equals the net coastal phytoplankton growth in all coastal regions except the Senegalo-Mauritanian area. Noticeably, in the Cape Blanc area, the net coastal phytoplankton growth is mostly sustained by high levels of regenerated production exceeding new production by more than twofold, which is in agreement with the locally weak input of nitrate by coastal upwelling. Further offshore, the distribution of nutrients and phytoplankton is explained by the coastal circulation. Indeed, in the northern part of our domain (i.e. Saharan Bank), the coastal circulation is mainly alongshore, resulting in low offshore lateral advection of nutrients and phytoplankton. Conversely, lateral advection transports coastal nutrients and phytoplankton towards offshore areas in the latitudinal band off the Senegalo-Mauritanian region. Moreover, this latter offshore region benefits from transient southern intrusions of nutrient-rich waters from the Guinean upwelling.

Eddy-resolving simulation of plankton ecosystem dynamics in the California Current System

NASA Astrophysics Data System (ADS)

Gruber, Nicolas; Frenzel, Hartmut; Doney, Scott C.; Marchesiello, Patrick; McWilliams, James C.; Moisan, John R.; Oram, John J.; Plattner, Gian-Kasper; Stolzenbach, Keith D.

2006-09-01

We study the dynamics of the planktonic ecosystem in the coastal upwelling zone within the California Current System using a three-dimensional (3-D), eddy-resolving circulation model coupled to an ecosystem/biogeochemistry model. The physical model is based on the Regional Oceanic Modeling System (ROMS), configured at a resolution of 15 km for a domain covering the entire US West Coast, with an embedded child grid covering the central California upwelling region at a resolution of 5 km. The model is forced with monthly mean boundary conditions at the open lateral boundaries as well as at the surface. The ecological/biogeochemical model is nitrogen based, includes single classes for phytoplankton and zooplankton, and considers two detrital pools with different sinking speeds. The model also explicitly simulates a variable chlorophyll-to-carbon ratio. Comparisons of model results with either remote sensing observations (AVHRR, SeaWiFS) or in-situ measurements from the CalCOFI program indicate that our model is capable of replicating many of the large-scale, time-averaged features of the coastal upwelling system. An exception is the underestimation of the chlorophyll levels in the northern part of the domain, perhaps because of the lack of short-term variations in the atmospheric forcing. Another shortcoming is that the modeled thermocline is too diffuse, and that the upward slope of the isolines toward the coast is too small. Detailed time-series comparisons with observations from Monterey Bay reveal similar agreements and discrepancies. We attribute the good agreement between the modeled and observed ecological properties in large part to the accuracy of the physical fields. In turn, many of the discrepancies can be traced back to our use of monthly mean forcing. Analysis of the ecosystem structure and dynamics reveal that the magnitude and pattern of phytoplankton biomass in the nearshore region are determined largely by the balance of growth and zooplankton grazing, while in the offshore region, growth is balanced by mortality. The latter appears to be inconsistent with in situ observations and is a result of our consideration of only one zooplankton size class (mesozooplankton), neglecting the importance of microzooplankton grazing in the offshore region. A comparison of the allocation of nitrogen into the different pools of the ecosystem in the 3-D results with those obtained from a box model configuration of the same ecosystem model reveals that only a few components of the ecosystem reach a local steady-state, i.e. where biological sources and sinks balance each other. The balances for the majority of the components are achieved by local biological source and sink terms balancing the net physical divergence, confirming the importance of the 3-D nature of circulation and mixing in a coastal upwelling system.

Upwelling characteristics in the Gulf of Finland (Baltic Sea) as revealed by Ferrybox measurements in 2007-2013

NASA Astrophysics Data System (ADS)

Kikas, Villu; Lips, Urmas

2016-07-01

Ferrybox measurements have been carried out between Tallinn and Helsinki in the Gulf of Finland (Baltic Sea) on a regular basis since 1997. The system measures autonomously water temperature, salinity, chlorophyll a fluorescence and turbidity and takes water samples for further analyses at a predefined time interval. We aimed to show how the Ferrybox technology could be used to study the coastal upwelling events in the Gulf of Finland. Based on the introduced upwelling index and related criteria, 33 coastal upwelling events were identified in May-September 2007-2013. The number of events, as well as the frequency of their occurrence and intensity expressed as a sum of daily average temperature deviations in the 20 km wide coastal area, were almost equal near the northern and southern coasts. Nevertheless, the wind impulse, which was needed to generate upwelling events of similar intensity, differed between the northern and southern coastal areas. It is suggested that the general thermohaline structure adapted to the prevailing forcing and the estuarine character of the basin weaken the upwelling created by the westerly to southwesterly (up-estuary) winds and strengthen the upwelling created by the easterly to northeasterly (down-estuary) winds. Two types of upwelling events were identified - one characterized by a strong temperature front and the other revealing gradual decrease in temperature from the open sea to the coastal area, with maximum temperature deviation close to the shore.

The physical oceanography of upwelling systems and the development of harmful algal blooms

PubMed Central

Pitcher, G.C.; Figueiras, F.G.; Hickey, B.M.; Moita, M.T.

2011-01-01

The upwelling systems of the eastern boundaries of the world’s oceans are susceptible to harmful algal blooms (HABs) because they are highly productive, nutrient-rich environments, prone to high-biomass blooms. This review identifies those aspects of the physical environment important in the development of HABs in upwelling systems through description and comparison of bloom events in the Benguela, California and Iberia systems. HAB development is dictated by the influence of wind stress on the surface boundary layer through a combination of its influence on surface mixed-layer characteristics and shelf circulation patterns. The timing of HABs is controlled by windstress fluctuations and buoyancy inputs at the seasonal, event and interannual scales. Within this temporal framework, various mesoscale features that interrupt typical upwelling circulation patterns, determine the spatial distribution of HABs. The inner shelf in particular provides a mosaic of shifting habitats, some of which favour HABs. Changes in coastline configuration and orientation, and bottom topography are important in determining the distribution of HABs through their influence on water stratification and retention. A spectrum of coastline configurations, including headlands, capes, peninsulas, Rías, bays and estuaries, representing systems of increasing isolation from the open coast and consequent increasing retention times, are assessed in terms of their vulnerability to HABs. PMID:22053120

A Model of the Spatial Structure and Productivity of Phytoplankton Populations during Variable Upwelling Off the Coast of Oregon

DTIC Science & Technology

1976-09-01

Univ., Corvallis, 71 p. barber, R. T. and J. H. Ryther, 1969. Organic chelators: factors affecting primary production in the Cromwell1 current upwelling...Mesoscale Air-Sea Interaction Group Technical Report I A MODEL OF THE SPATIAL STRUCTURE AND PRODUCTIVITY OF PHYTOPLANKTON POPULATIONS DURING...Variability in the wind stress affects the rate of ufpwelling and ultimtely the local biological productivity . To investigate the relationship between wind

Variability of the internal tide on the southern Monterey Bay continental shelf and associated bottom boundary layer sediment transport

USGS Publications Warehouse

Rosenberger, Kurt; Storlazzi, Curt; Cheriton, Olivia

2016-01-01

A 6-month deployment of instrumentation from April to October 2012 in 90 m water depth near the outer edge of the mid-shelf mud belt in southern Monterey Bay, California, reveals the importance regional upwelling on water column density structure, potentially accounting for the majority of the variability in internal tidal energy flux across the shelf. Observations consisted of time-series measurements of water-column currents, temperature and salinity, and near-bed currents and suspended matter. The internal tide accounted for 15–25% of the water-column current variance and the barotropic tide accounted for up to 35%. The subtidal flow showed remarkably little shear and was dominated by the 7–14 day band, which is associated with relaxations in the dominant equatorward winds typical of coastal California in the spring and summer. Upwelling and relaxation events resulted in strong near-bed flows and accounted for almost half of the current stress on the seafloor (not accounting for wave orbital velocities), and may have driven along-shelf geostrophic flow during steady state conditions. Several elevated suspended particulate matter (SPM) events occurred within 3 m of the bed and were generally associated with higher, long-period surface waves. However, these peaks in SPM did not coincide with the predicted resuspension events from the modeled combined wave–current shear stress, indicating that the observed SPM at our site was most likely resuspended elsewhere and advected along-isobath. Sediment flux was almost equal in magnitude in the alongshore and cross-shore directions. Instances of wave–current shear stress that exceeded the threshold of resuspension for the silty-clays common at these water depths only occurred when near-bed orbital velocities due to long-period surface waves coincided with vigorous near-bed currents associated with the internal tide or upwelling/relaxation events. Thus upwelling/relaxation dynamics are primarily responsible for variability in the internal tide, as well as transport of near-bottom sediment in the mid-self mud belt during the relatively quiescent summer months.

Microbial Diversity of a Brazilian Coastal Region Influenced by an Upwelling System and Anthropogenic Activity

PubMed Central

Cury, Juliano C.; Araujo, Fabio V.; Coelho-Souza, Sergio A.; Peixoto, Raquel S.; Oliveira, Joana A. L.; Santos, Henrique F.; Dávila, Alberto M. R.; Rosado, Alexandre S.

2011-01-01

Background Upwelling systems are characterised by an intense primary biomass production in the surface (warmest) water after the outcrop of the bottom (coldest) water, which is rich in nutrients. Although it is known that the microbial assemblage plays an important role in the food chain of marine systems and that the upwelling systems that occur in southwest Brazil drive the complex dynamics of the food chain, little is known about the microbial composition present in this region. Methodology/Principal Findings We carried out a molecular survey based on SSU rRNA gene from the three domains of the phylogenetic tree of life present in a tropical upwelling region (Arraial do Cabo, Rio de Janeiro, Brazil). The aim was to analyse the horizontal and vertical variations of the microbial composition in two geographically close areas influenced by anthropogenic activity (sewage disposal/port activity) and upwelling phenomena, respectively. A lower estimated diversity of microorganisms of the three domains of the phylogenetic tree of life was found in the water of the area influenced by anthropogenic activity compared to the area influenced by upwelling phenomena. We observed a heterogenic distribution of the relative abundance of taxonomic groups, especially in the Archaea and Eukarya domains. The bacterial community was dominated by Proteobacteria, Cyanobacteria and Bacteroidetes phyla, whereas the microeukaryotic community was dominated by Metazoa, Fungi, Alveolata and Stramenopile. The estimated archaeal diversity was the lowest of the three domains and was dominated by uncharacterised marine Crenarchaeota that were most closely related to Marine Group I. Conclusions/Significance The variety of conditions and the presence of different microbial assemblages indicated that the area of Arraial do Cabo can be used as a model for detailed studies that contemplate the correlation between pollution-indicating parameters and the depletion of microbial diversity in areas close to anthropogenic activity; functional roles and geochemical processes; phylogeny of the uncharacterised diversity; and seasonal variations of the microbial assemblages. PMID:21304582

Upwelling Radiance at 976 nm Measured from Space Using a CCD Camera

NASA Technical Reports Server (NTRS)

Biswas, Abhijit; Kovalik, Joseph M.; Oaida, Bogdan V.; Abrahamson, Matthew J.; Wright, Malcolm W.

2015-01-01

The Optical Payload for Lasercomm Science (OPALS) Flight System on-board the International Space Station uses a charge coupled device (CCD) camera for receiving a beacon laser from Earth. Relative measurements of the background contributed by upwelling radiance under diverse illumination conditions and varying terrain is presented. In some cases clouds in the field-of-view allowed a comparison of terrestrial and cloud-top upwelling radiance. In this paper we will report these measurements and examine the extent of agreement with atmospheric model predictions.

Intensification of upwelling along Oman coast in a warming scenario

NASA Astrophysics Data System (ADS)

Praveen, V.; Ajayamohan, R. S.; Valsala, V.; Sandeep, S.

2016-07-01

The oceanic impact of poleward shift in monsoon low-level jet (MLLJ) is examined using a Regional Ocean Modeling System (ROMS). Two sets of downscaling experiments were conducted using ROMS with boundary and initial conditions from six CMIP5 models. While outputs from the historical run (1981-2000) acts as forcing for the first, the second uses RCP8.5 (2080-2099). By comparing the outputs, it is found that Oman coast will experience an increase in upwelling in tune with MLLJ shift. Consistent with the changes in upwelling and zonal Ekman transport, temperature, salinity, and productivity show significant changes near the Oman coast. The changes in MLLJ causes the coastal wind to angle against the Oman coast in such a fashion that the net upwelling increases in the next century and so does the marine productivity. This study contrasts the general view of weakening of upwelling along the Arabian coasts due to the weakening of monsoon winds.

A note on specific variability of long surface gravity waves and drag coefficient in coastal upwelling zone

NASA Astrophysics Data System (ADS)

Krzyścin, Janusz

1990-01-01

In this paper we solve analytically wave kinematic equations and the wave energy transport equation, for basic long surface gravity wave in the coastal upwelling zone. Using Gent and Taylor's (1978) parameterization of drag coefficient (which includes interaction between long surface waves and the air flow) we find variability of this coefficient due to wave amplification and refraction caused by specific surface water current in the region. The drag coefficient grows towards the shore. The growth is faster for stronger current. When the angle between waves and the current is less than 90° the growth is mainly connected with the waves steepness, but when the angle is larger, it is caused by relative growth of the wave phase velocity.

Do submesoscale frontal processes ventilate the oxygen minimum zone off Peru?

NASA Astrophysics Data System (ADS)

Thomsen, S.; Kanzow, T.; Colas, F.; Echevin, V.; Krahmann, G.; Engel, A.

2016-08-01

The Peruvian upwelling system encompasses the most intense and shallowest oxygen minimum zone (OMZ) in the ocean. This system shows pronounced submesoscale activity like filaments and fronts. We carried out glider-based observations off Peru during austral summer 2013 to investigate whether submesoscale frontal processes ventilate the Peruvian OMZ. We present observational evidence for the subduction of highly oxygenated surface water in a submesoscale cold filament. The subduction event ventilates the oxycline but does not reach OMZ core waters. In a regional submesoscale-permitting model we study the pathways of newly upwelled water. About 50% of upwelled virtual floats are subducted below the mixed layer within 5 days emphasizing a hitherto unrecognized importance of subduction for the ventilation of the Peruvian oxycline.

Effect of Interannual Variability on the Ocean Acidification-induced Habitat Restriction of the Humboldt Current System.

NASA Astrophysics Data System (ADS)

Franco, A. C.; Gruber, N.; Munnich, M.

2016-02-01

The Humboldt Current System (HCS) is one of the most productive ecosystems in the world. This high productivity is supported by a large input of nutrients from the subsurface layers to the surface due to year-round upwelling. However, upwelling also supplies waters with low pH and low aragonite saturation state potentially affecting many organisms, especially those that calcify. The influence, extent and source of upwelled water varies substantially on interannual timescales in association with the El Niño/Southern Oscillation (ENSO) phenomenon, accentuating productivity during La Niña events and dampening it during El Niño, altering the dynamics of the whole ecosystem. On top of this natural variability, the continuing acidification of the upper ocean in response to raising atmospheric CO2 may decrease pH further and increase the volume of water corrosive to aragonite in this region, leading to a progressively smaller suitable habitat for sensitive organisms. Here we use an eddy-resolving basin-scale ocean model that covers the whole Pacific Ocean with higher resolution near the coast off South America ( 6 km) to investigate the role of ENSO events on low aragonite saturation episodes and productivity variations. We compare 2 simulations: a hindcast simulation that spans the last 30 years and a future scenario that represents year 2090 (following IPCC's "business-as-usual" scenario). We found that in the region off Peru, the sole effect of increasing atmospheric CO2 to 840 matm shoals the annual average aragonite saturation depth to 30 m, creating a year round presence of aragonite undersaturated water in the euphotic zone. We then contrast the effect on primary productivity and the aragonite saturation state of at least eight El Niño and eight La Niña episodes that have been reported for the past 30 years, in an attempt to answer the question: does habitat availability under future ocean acidification will resemble a pervasive La Niña-like state?

The Arabian Sea as a high-nutrient, low-chlorophyll region during the late Southwest Monsoon

NASA Astrophysics Data System (ADS)

Naqvi, S. W. A.; Moffett, J. W.; Gauns, M. U.; Narvekar, P. V.; Pratihary, A. K.; Naik, H.; Shenoy, D. M.; Jayakumar, D. A.; Goepfert, T. J.; Patra, P. K.; Al-Azri, A.; Ahmed, S. I.

2010-01-01

Extensive observations during the late Southwest Monsoon of 2004 over the Indian and Omani shelves, and along an east-west transect reveal a mosaic of biogeochemical provinces including an unexpected high-nutrient, low-chlorophyll condition off the southern Omani coast. This feature, coupled with other characteristics of the system, suggest a close similarity between the Omani upwelling system and the Peruvian and California upwelling systems, where primary production (PP) is limited by iron. An intensification of upwelling, reported to have been caused by the decline in the winter/spring Eurasian snow cover since 1997, is not supported by in situ hydrographic and chlorophyll measurements as well as a reanalysis of ocean colour data extending to 2009. Iron limitation of PP may complicate simple relationship between upwelling and PP assumed by previous workers, and contribute to the anomalous offshore occurrence of the most severe oxygen (O2) depletion in the region. Over the Indian shelf, affected by very shallow O2-deficient zone, high PP is restricted to a thin, oxygenated surface layer probably due to unsuitability of the O2-depleted environment for the growth of oxygenic photosynthesizers.

Coastal Jets, Oceanic Upwelling, Mesoscale Eddies, and Clouds in the Southeast Pacific

NASA Astrophysics Data System (ADS)

Hong, X.; Wang, S.; Jiang, Q.; O'Neill, L. W.; Hodur, R.; Chen, S.; Martin, P.; Cummings, J. A.

2009-12-01

Coastal jets, oceanic upwelling, mesoscale eddies, and clouds in the Southeast Pacific (SEP) are studied using the two-way-coupled COAMPS/NCOM system with the NCODA for the ocean data assimilation. The coupled system was run for the period of the VAMOS Ocean-Cloud-Atmosphere-Land Study (VOCALS) field campaign from 20 October to 30 November, 2008. The investigation of the feedback between the atmosphere and the ocean is focused on the periods of the strong and the weak coastal jets. During the strong coastal jet period, colder and drier air along the coast results in larger surface heat fluxes and increased boundary layer height. More extensive and organized clouds are generated in the strongly unstable conditions in the atmospheric boundary layer. The oceanic upwelling is stronger and the upwelled cold water extends further offshore. During the weak coastal jet period, the cyclonic and anti-cyclonic oceanic eddies propagate westward more significantly. The inertial oscillations induced by the variations of the wind stress also increase in strength with stronger phase shifts between the oscillations in the upper and the lower layers of the ocean. In addition, the model results from the coupled system were evaluated with available observations from the VOCALS field campaign.

Seasonal variation of the South Indian tropical gyre

NASA Astrophysics Data System (ADS)

Aguiar-González, Borja; Ponsoni, Leandro; Ridderinkhof, Herman; van Aken, Hendrik M.; de Ruijter, Will P. M.; Maas, Leo R. M.

2016-04-01

Based on satellite altimeter data and global atlases of temperature, salinity, wind stress and wind-driven circulation we investigate the seasonal variation of the South Indian tropical gyre and its associated open-ocean upwelling system, known as the Seychelles-Chagos Thermocline Ridge (SCTR). Results show a year-round, altimeter-derived cyclonic gyre where the upwelling regime appears closely related to seasonality of the ocean gyre, a relationship that has not been previously explored in this region. An analysis of major forcing mechanisms suggests that the thermocline ridge results from the constructive interaction of basin-scale wind stress curl, local-scale wind stress forcing and remote forcing driven by Rossby waves of different periodicity: semiannual in the west, under the strong influence of monsoonal winds; and, annual in the east, where the southeasterlies prevail. One exception occurs during winter, when the well-known westward intensification of the upwelling core, the Seychelles Dome, is shown to be largely a response of the wind-driven circulation. At basin-scale, the most outstanding feature is the seasonal shrinkage of the ocean gyre and the SCTR. From late autumn to spring, the eastward South Equatorial Countercurrent (SECC) recirculates early in the east on feeding the westward South Equatorial Current, therefore closing the gyre before arrival to Sumatra. We find this recirculation longitude migrates over 20° and collocates with the westward advance of a zonal thermohaline front emerging from the encounter between (upwelled) Indian Equatorial Water and relatively warmer and fresher Indonesian Throughflow Water. We suggest this front, which we call the Indonesian Throughflow Front, plays an important role as remote forcing to the tropical gyre, generating southward geostrophic flows that contribute to the early recirculation of the SECC.

Monsoon Variability in the Arabian Sea from Enhanced and Standard Horizontal Resolution Coupled Climate Models.

NASA Astrophysics Data System (ADS)

McClean, J.; Veneziani, C.; Maltrud, M. E.; Taylor, M.; Bader, D. C.; Branstetter, M. L.; Evans, K. J.; Mahajan, S.

2016-02-01

The circulation of the upper ocean in the Arabian Sea switches direction seasonally due to the change in direction of the prevailing winds associated with the Indian Monsoon. Predictability of the monsoon circulation, however, is uncertain due to incomplete understanding of the physical processes operating on the monsoon and other time scales, particularly interannual and intraseasonal. We use the Community Earth System Model (CESM) with enhanced horizontal resolution in each of its components relative to standard coupled climate model resolution, to better understand these time scale interactions. A standard resolution CESM counterpart is used to assess how horizontal resolution impacts the depiction of these processes. In the enhanced resolution case, 0.25° Community Atmosphere Model 5 (CAM5) is coupled to, among other components, the tripolar nominal 0.1° Parallel Ocean Program 2 (POP2). The fine resolution CESM simulation was run for 85 years; constant 1850 preindustrial forcing was used throughout the run, allowing us to isolate internal variability of the coupled system. Model parameters were adjusted ("tuned") to produce an acceptably small top of the atmosphere radiation imbalance. The reversal of the Somali Current (SC), the western boundary current off northeast Africa, has typically been associated with that of the monsoon. The SC reverses from southwestward in boreal winter to northeastward in summer; coastal upwelling is induced by the summer monsoonal winds. Recently it has been shown from new observations that the SC starts to reverse prior to the monsoon switch. Westward propagating Rossby waves have been implicated as responsible for the early SC reversal. We will discuss the sequencing of remote and local forcing on the timing of the spring inter-monsoonal switch in the direction of the SC and the appearance of the Great Whirl off the Oman Coast. Particularly, we consider how the Indian Ocean Dipole (IOD) acts to modify the seasonal strength and variability of the western boundary current system including upwelling. We look for a connection between interannual upwelling variability and that of rainfall off the west coast of India. As well, we examine changes due to the IOD in the upper ocean temperature and salinity structure along the Rossby wave propagation route in the Arabian Sea.

Implications of Upwells as Hydrodynamic Jets in a Pulse Jet Mixed System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pease, Leonard F.; Bamberger, Judith A.; Minette, Michael J.

2015-08-01

This report evaluates the physics of the upwell flow in pulse jet mixed systems in the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Although the initial downward flow and radial flow from pulse jet mixers (PJMs) has been analyzed in some detail, the upwells have received considerably less attention despite having significant implications for vessel mixing. Do the upwells behave like jets? How do the upwells scale? When will the central upwell breakthrough? What proportion of the vessel is blended by the upwells themselves? Indeed, how the physics of the central upwell is affected by multiple PJMs (e.g., sixmore » in the proposed mixing vessels), non-Newtonian rheology, and significant multicomponent solids loadings remain unexplored. The central upwell must satisfy several criteria to be considered a free jet. First, it must travel for several diameters in a nearly constant direction. Second, its velocity must decay with the inverse of elevation. Third, it should have an approximately Gaussian profile. Fourth, the influence of surface or body forces must be negligible. A combination of historical data in a 12.75 ft test vessel, newly analyzed data from the 8 ft test vessel, and conservation of momentum arguments derived specifically for PJM operating conditions demonstrate that the central upwell satisfies these criteria where vigorous breakthrough is achieved. An essential feature of scaling from one vessel to the next is the requirement that the underlying physics does not change adversely. One may have confidence in scaling if (1) correlations and formulas capture the relevant physics; (2) the underlying physics does not change from the conditions under which it was developed to the conditions of interest; (3) all factors relevant to scaling have been incorporated, including flow, material, and geometric considerations; and (4) the uncertainty in the relationships is sufficiently narrow to meet required specifications. Although the central upwell satisfies these criteria when vigorous breakthrough is achieved, not all available data follow the free jet profile for the central upwell, particularly at lower nozzle velocities. Alternative flow regimes are considered and new models for cloud height, “cavern height,” and the rate of jet penetration (jet celerity) are benchmarked against data to anchor scaling analyses. This analytical modeling effort to provide a technical basis for scaling PJM mixed vessels has significant implications for vessel mixing, because jet physics underlies “cavern” height, cloud height, and the volume of mixing considerations. A new four-parameter cloud height model compares favorably to experimental results. This model is predictive of breakthrough in 8 ft vessel tests with the two-part simulant. Analysis of the upwell in the presence of yield stresses finds evidence of expanding turbulent jets, confined turbulent jets, and confined laminar flows. For each, the critical elevation at which jet momentum depletes is predicted, which compare favorably to experimental cavern height data. Partially coupled momentum and energy balances suggest that these are limiting cases of a gradual transition from a turbulent expanding flow to a confined laminar flow. This analysis of the central upwell alone lays essential groundwork for complete analysis of mode three mixing (i.e., breakthrough with slow peripheral mixing). Consideration of jet celerity shows that the rate of jet penetration is a governing consideration in breakthrough to the surface. Estimates of the volume of mixing are presented. This analysis shows that flow along the vessel wall is sluggish such that the central upwell governs the volume of mixing. This analysis of the central upwell alone lays essential groundwork for complete analysis of mode three mixing and estimates of hydrogen release rates from first principles.« less

Local wind forcing of the Monterey Bay area inner shelf

USGS Publications Warehouse

Drake, P.T.; McManus, M.A.; Storlazzi, C.D.

2005-01-01

Wind forcing and the seasonal cycles of temperature and currents were investigated on the inner shelf of the Monterey Bay area of the California coast for 460 days, from June 2001 to September 2002. Temperature measurements spanned an approximate 100 km stretch of coastline from a bluff just north of Monterey Bay south to Point Sur. Inner shelf currents were measured at two sites near the bay's northern shore. Seasonal temperature variations were consistent with previous observations from the central California shelf. During the spring, summer and fall, a seasonal mean alongshore current was observed flowing northwestward in the northern bay, in direct opposition to a southeastward wind stress. A barotropic alongshore pressure gradient, potentially driving the northwestward flow, was needed to balance the alongshore momentum equation. With the exception of the winter season, vertical profiles of mean cross-shore currents were consistent with two-dimensional upwelling and existing observations from upwelling regions with poleward subsurface flow. At periods of 15-60 days, temperature fluctuations were coherent both throughout the domain and with the regional wind field. Remote wind forcing was minimal. During the spring upwelling season, alongshore currents and temperatures in the northern bay were most coherent with winds measured at a nearby land meteorological station. This wind site showed relatively low correlations to offshore buoy wind stations, indicating localized wind effects are important to the circulation along this stretch of Monterey Bay's inner shelf. ?? 2004 Elsevier Ltd. All rights reserved.

Across-shelf variability of phytoplankton composition, photosynthetic parameters and primary production in the NW Iberian upwelling system

NASA Astrophysics Data System (ADS)

Lorenzo, Luisa M.; Arbones, Belén; Tilstone, Gavin H.; Figueiras, Francisco G.

2005-02-01

Hydrographic conditions, phytoplankton composition and biomass, photosynthetic parameters and primary production were determined in the Ría de Vigo and adjacent shelf waters during April-May 1997 and September 1998. The sampling was designed to find the seasonal downwelling-upwelling and upwelling-downwelling transition periods characteristic of spring and autumn phytoplankton blooms. There was upwelling relaxation event followed by downwelling during both spring and autumn cruises. Temperature and salinity distributions showed that ría and shelf waters formed two distinct domains, which were separated by a thermohaline front at the mouth of the ría. The phytoplankton composition was completely different in the two environments. Cyanobacteria dominated on the shelf and constituted 46-66% of total phytoplankton biomass, while large phytoplankton (diatoms and dinoflagellates) were more abundant in the ría, especially during upwelling relaxation. However, the high shelf-ría exchange induced by a strong downwelling event on 7 September 1998 removed large phytoplankton (mainly diatoms) from the water column in the ría. Chlorophyll-specific maximum photosynthetic rates ( PmB) were significantly higher in the ría domain during upwelling relaxation, when autotrophic microplankton dominated in the interior. Primary production varied from 0.63 to 2.6 g C m -2 day -1 during the spring cruise and between 0.32 and 2.09 g C m -2 day -1 during the autumn cruise, with the highest values in the ría during both cruises. Primary production was relatively constant on the shelf with no significant differences between cruises, whereas differences were significant in the ría, with higher values during upwelling relaxation periods and lower values during downwelling. Analysis of light saturation parameters and light absorbed by phytoplanton in the water column suggests that photosynthesis was not light-limited either on the shelf or in the ría. It is concluded that upwelling-downwelling cycles were the main driving force, through changes in autotrophic microplankton biomass in the ría, that caused the variability observed in the ría-shelf system.

Mindanao Dome variability over the last 160 kyr: Episodic glacial cooling of the West Pacific Warm Pool

NASA Astrophysics Data System (ADS)

Bolliet, Timothé; Holbourn, Ann; Kuhnt, Wolfgang; Laj, Carlo; Kissel, Catherine; Beaufort, Luc; Kienast, Markus; Andersen, Nils; Garbe-Schönberg, Dieter

2011-02-01

We present sea surface, upper thermocline, and benthic δ18O data, as well as temperature and paleoproductivity proxy data, from the International Marine Global Change Study Program (IMAGES) Core MD06-3067 (6°31‧N, 126°30‧E, 1575 m water depth), located in the western equatorial Pacific Ocean within the flow path of the Mindanao Current. Our records reveal considerable glacial-interglacial and suborbital variability in the Mindanao Dome upwelling over the last 160 kyr. Dome activity generally intensified during glacial intervals resulting in cooler thermocline waters, whereas it substantially declined during interglacials, in particular in the early Holocene and early marine oxygen isotope stage (MIS) 5e, when upwelling waters did not reach the thermocline. During MIS 3 and MIS 2, enhanced surface productivity together with remarkably low SST and low upper ocean thermal contrast provide evidence for episodic glacial upwelling to the surface, whereas transient surface warming marks periodic collapses of the Mindanao Dome upwelling during Heinrich events. We attribute the high variability during MIS 3 and MIS 2 to changes in the El Niño Southern Oscillation state that affected boreal winter monsoonal winds and upper ocean circulation. Glacial upwelling intensified when a strong cyclonic gyre became established, whereas El Niño-like conditions during Heinrich events tended to suppress the cyclonic circulation, reducing Ekman transport. Thus, our findings demonstrate that variations in the Mindanao Dome upwelling are closely linked to the position and intensity of the tropical convection and also reflect far-field influences from the high latitudes.

Modeling new production in upwelling centers - A case study of modeling new production from remotely sensed temperature and color

NASA Technical Reports Server (NTRS)

Dugdale, Richard C.; Wilkerson, Frances P.; Morel, Andre; Bricaud, Annick

1989-01-01

A method has been developed for estimating new production in upwelling systems from remotely sensed surface temperatures. A shift-up model predicts the rate of adaptation of nitrate uptake. The time base for the production cycle is obtained from a knowledge of surface heating rates and differences in temperature between the point of upwelling and each pixel. Nitrate concentrations are obtained from temperature-nitrate regression equations. The model was developed for the northwest Africa upwelling region, where shipboard measurements of new production were available. It can be employed in two modes, the first using only surface temperatures, and the second in which CZCS color data are incorporated. The major advance offered by this method is the capability to estimate new production on spatial and time scales inaccessible with shipboard approaches.

Short-term meso-scale variability of mesozooplankton communities in a coastal upwelling system (NW Spain)

NASA Astrophysics Data System (ADS)

Roura, Álvaro; Álvarez-Salgado, Xosé A.; González, Ángel F.; Gregori, María; Rosón, Gabriel; Guerra, Ángel

2013-02-01

The short-term, meso-scale variability of the mesozooplankton community present in the coastal upwelling system of the Ría de Vigo (NW Spain) has been analysed. Three well-defined communities were identified: coastal, frontal and oceanic, according to their holoplankton-meroplankton ratio, richness, and total abundance. These communities changed from summer to autumn due to a shift from downwelling to upwelling-favourable conditions coupled with taxa dependent changes in life strategies. Relationships between the resemblance matrix of mesozooplankton and the resemblance matrices of meteorologic, hydrographic and community-derived biotic variables were determined with distance-based linear models (DistLM, 18 variables), showing an increasing amount of explained variability of 6%, 16.1% and 54.5%, respectively. A simplified model revealed that the variability found in the resemblance matrix of mesozooplankton was mainly described by the holoplankton-meroplankton ratio, the total abundance, the influence of lunar cycles, the upwelling index and the richness; altogether accounting for 64% of the total variability. The largest variability of the mesozooplankton resemblance matrix (39.6%) is accounted by the holoplankton-meroplankton ratio, a simple index that describes appropriately the coastal-ocean gradient. The communities described herein kept their integrity in the studied upwelling and downwelling episodes in spite of the highly advective environment off the Ría de Vigo, presumably due to behavioural changes in the vertical position of the zooplankton.

Export of pre-aged, labile DOM from a central California coastal upwelling system: Insights from D/L amino acids and Δ14C signatures

NASA Astrophysics Data System (ADS)

Walker, B. D.; Shen, Y.; Benner, R. H.; Druffel, E. R. M.

2014-12-01

Coastal upwelling zones are among the most productive regions in the world and play a major role in global carbon and nitrogen cycles. Recent research suggests that a substantial fraction of newly fixed organic matter is exported offshore in the form of dissolved organic matter (DOM). However, to date only a few studies have examined DOM composition in the context of production and export from upwelling systems. The ultimate fate and geochemical impact of coastal DOM exported to offshore and mesopelagic ecosystems also remains largely unknown. Between 2007-2009 we conducted a high-resolution biogeochemical time series at the Granite Canyon Marine Pollution Studies Lab in part to evaluate the seasonal production and export of DOM from the Central CA coast. Our previous work demonstrated substantial, albeit disparate, seasonal production of dissolved organic carbon and nitrogen (DOC, DON) - with high DON (and low C:N ratios) produced during upwelling and high DOC produced during summer/fall water column stratification (Walker and McCarthy, 2012). Here we present new total dissolved D/L amino acid (TDAA) and UV-oxidizable DOC radiocarbon (Δ14C) data with the goal of determining the relative sources (heterotrophic vs. autotrophic), bioavailability, microbial processing and 14C-ages of C-rich vs. N-rich DOM exported from this upwelling system. Our results suggest that C-rich DOM produced during water column stratification carries a large microbial signature (i.e. high D/L AA ratios and non-protein AA abundance), whereas N-rich DOM produced during upwelling appears to be fresh, autotrophic DOM (i.e. lowest D/L AA ratios and highest TDAA abundance). DOM Δ14C signatures also did not approximate in situ dissolved inorganic carbon (DIC), and instead were far more negative and highly correlated to water mass density. Together our results indicate a previously unrecognized source of highly labile yet pre-aged DOM potentially impacting offshore and mesopelagic ecosystems.

Modelling the upwelling offthe east Hainan Island coast in summer 2010

NASA Astrophysics Data System (ADS)

Bai, Peng; Gu, Yanzhen; Li, Peiliang; Wu, Kejian

2016-11-01

A synoptic-scale upwelling event that developed offthe east coast of the Hainan Island (EHIU) in the summer of 2010 is defined well via processing the Moderate Resolution Imaging Spectroradiometer (MODIS) sea surface temperature (SST) data. The Regional Ocean Modeling System (ROMS) with high spatial resolution has been used to investigate this upwelling event. By comparing the ROMS results against tide station data, Argo float profiles and MODIS SST, it is confirmed that the ROMS reproduces the EHIU well. The cooler-water core (CWC) distinguished by waters < 27.5°C in the EHIU, which occurred in the east Qiongzhou Strait mouth area and was bounded by a high temperature gradient, was the focus of this paper. Vertical structure of the CWC suggests that interaction between the westward flow and the bathymetry slope played a significant role in the formation of CWC. Numerical experiments indicated that the westward flow in the Qiongzhou Strait was the result of tidal rectification over variable topography (Shi et al., 2002), thus tides played a critical role on the development of the CWC. The negative wind stress curl that dominated the east Qiongzhou Strait mouth area suppressed the intensity of the CWC by 0.2-0.4°C. Further, nonlinear interaction between tidal currents and wind stress enhanced vertical mixing greatly, which would benefit the development of the CWC.

Acidification mediated by a river plume and coastal upwelling on a fringing reef at the east coast of Hainan Island, Northern South China Sea

NASA Astrophysics Data System (ADS)

Dong, Xu; Huang, Haining; Zheng, Nan; Pan, Aijun; Wang, Sumin; Huo, Cheng; Zhou, Kaiwen; Lin, Hui; Ji, Weidong

2017-09-01

We investigated the dynamics of carbonate system which was greatly modulated by a river plume and coastal upwelling in July 2014 and July 2015 at the east coast of Hainan Island where a fringing reef distributes inshore. By using a three end-member mixing model, we semiquantitatively estimated the removal of dissolved inorganic carbon (DIC) mediated by biological production in the river plume and upwelled water to be 13 ± 17 and 15 ± 16 μmol kg-1, respectively. The enhanced organic production was mainly responsible for these DIC consumptions in both two regimes, however, nearly a half of DIC removal was attributed to biocalcification in the plume system while it was negligible in the upwelling system. Furthermore, the modeled results over reefs revealed that river plume and coastal upwelling were two major threats of acidification to coral communities at the east coast of Hainan Island during cruises. In comparison, the biological contribution to acidification was limited for balancing between organic production and biocalcification during July 2014 cruise, whereas the acidification was greatly intensified by organic degradation during July 2015 cruise. It was verified that naturally local acidification (physical and biological processes) played a major role in great pH decreases on a short-term scale, leading to coastal waters more vulnerable to anthropogenic "ocean acidification" (uptake of atmospheric CO2) by reducing buffering capacity of waters. Finally, effects of acidification associated with other local threats on a fringing reef were further depicted with a conceptual model.

The role of Southern Ocean mixing and upwelling in glacial-interglacial atmospheric CO2 change

NASA Astrophysics Data System (ADS)

Watson, Andrew J.; Naveira Garabato, Alberto C.

2006-02-01

Decreased ventilation of the Southern Ocean in glacial time is implicated in most explanations of lower glacial atmospheric CO2. Today, the deep (>2000 m) ocean south of the Polar Front is rapidly ventilated from below, with the interaction of deep currents with topography driving high mixing rates well up into the water column. We show from a buoyancy budget that mixing rates are high in all the deep waters of the Southern Ocean. Between the surface and ~2000 m depth, water is upwelled by a residual meridional overturning that is directly linked to buoyancy fluxes through the ocean surface. Combined with the rapid deep mixing, this upwelling serves to return deep water to the surface on a short time scale. We propose two new mechanisms by which, in glacial time, the deep Southern Ocean may have been more isolated from the surface. Firstly, the deep ocean appears to have been more stratified because of denser bottom water resulting from intense sea ice formation near Antarctica. The greater stratification would have slowed the deep mixing. Secondly, subzero atmospheric temperatures may have meant that the present-day buoyancy flux from the atmosphere to the ocean surface was reduced or reversed. This in turn would have reduced or eliminated the upwelling (contrary to a common assumption, upwelling is not solely a function of the wind stress but is coupled to the air-sea buoyancy flux too). The observed very close link between Antarctic temperatures and atmospheric CO2 could then be explained as a natural consequence of the connection between the air-sea buoyancy flux and upwelling in the Southern Ocean, if slower ventilation of the Southern Ocean led to lower atmospheric CO2. Here we use a box model, similar to those of previous authors, to show that weaker mixing and reduced upwelling in the Southern Ocean can explain the low glacial atmospheric CO2 in such a formulation.

The Effects of Climatological and Transient Wind Forcing on Eddy Generation in the California Current System

DTIC Science & Technology

1989-09-01

most dynamically important area in the coastal upwelling region (Philander and Yoon, 1982; Allen, 1980) and as such, the treatment of this region becomes...the area of the model domain (Nelson, 1977). This treatment of the wind stress eliminates all spatial variability in the nearshore region, reducing...that of Experiment 3, again using data from Nelson (1977). The difference in the two experiments lies in the treatment of the wind field next to the

Isotopic and enzymatic analyses of planktonic nitrogen utilisation in the vicinity of Cape Sines (Portugal) during weak upwelling activity

NASA Astrophysics Data System (ADS)

Slawyk, Gerd; Coste, Bernard; Collos, Yves; Rodier, Martine

1997-01-01

Using measurements of 15N uptake and activities of nitrate reductase and glutamine synthetase, the utilization of nitrogenous nutrients by microplankton in the Portuguese upwelling area was investigated. During this cruise the euphotic zone of coastal waters was in most cases bisected by a nitracline forming two layers. Total inorganic nitrogen uptake rates (NH 4+ + NO 3-) in the upper mixed and nitrate-impoverished layer ranged from 0.1 to 0.8 nM h -1 and were primarily supported by regenerated (ammonium) nitrogen (62-97%), whereas they varied between 0.9 and 10.4 nM h -1 in the deep nitrate-rich layer and were mainly driven by new (nitrate) nitrogen (52-82%). Depth profiles of Chl a-specific uptake rates for ammonium and nitrate paralleled those of absolute uptake rates, i.e. values of VNH 4+Chl were highest (up to 16.1 nmol μg -1 h -1) in nitrate-poor surface waters while values of VNO 3-Chl were maximum (up to 8.4 nmol μg -1 h -1)within the nitracline. This latter vertical ordering of planktonic nitrogen nutrition was consistent with an aged upwelling situation. However, applying several indices of cell metabolism and nutritional status, such as 15N uptake/enzyme activity, surge uptake internally controlled uptake, and V maxChl/K t ratios, we were able to demonstrate that the phytoplankton assemblages inhabiting the nutrient-impoverished upper layer still bore the signature of physically mediated nitrogen (nitrate) supply generated by active upwelling that had occurred during the week before our visit to the area. This signature was the most evident in samples from the station furthest inshore and faded with distance from shore as a result of the deepening of the nitrate isopleths (weakening of upwelling activity), which showed the same offshore trend. The appearance of nitrate-rich waters at the surface, after a strong pulse of upwelling favourable winds just before the end of the cruise, led to a five-fold increase in average (over the euphotic zone) absolute and Chl a-specific nitrate uptake rates (10.4 nM h -1, 7.5 nmol μ -1 h -1) compared to the mean rates during weak upwelling (1.7 nM h -1, 1.5 nmol μ -1 h -1). From a comparison with the neighbouring Moroccan upwelling, it is assumed that new production in the Portuguese upwelling averages 50 nM h -1. Thus, this upwelling would rank with the northwest African upwelling system off Cape Blanc or with the Californian upwelling at Point Conception for the capacity of new production, but seems to be much less efficient (seven-fold) than the highly permanent Peru upwelling.

Short-term alteration of biotic and abiotic components of the pelagic system in a shallow bay produced by a strong natural hypoxia event

PubMed Central

Veas, Rodrigo; Anabalón, Valeria; Quiñones, Renato A.

2017-01-01

In January 2008 there was an intensive and extensive upwelling event in the southern Humboldt Current System. This event produced an intrusion of water with low dissolved oxygen into Coliumo Bay, which caused massive mortality and the beaching of pelagic and benthic organisms, including zooplankton. During this event, which lasted 3 to 5 days, we studied and evaluated the effect of the hypoxic water in the bay on the abundance of macrozooplankton, nanoplankton and microphytoplankton, the concentration of several nutrients and hydrographic conditions. At the beginning of the hypoxia event the water column had very low dissolved oxygen concentrations (<0.5 mL O2 L-1), low temperatures and high salinity which are characteristics of the oxygen minimum zone from the Humboldt Current System. Redox, pH, nitrate, phosphate, silicate and chlorophyll-a values were the lowest, while nitrate and the phaeopigment values were the highest. The N:P ratio was below 16, and the abundance of nano- and microphytoplankton were at their lowest, the latter also with the lowest proportion of live organisms. Macrozooplankton had the greatest abundance during hypoxia, dominated mainly by crustacean, fish eggs and amphipods. The hypoxia event generated a strong short-term alteration of all biotic and abiotic components of the pelagic system in Coliumo Bay and the neighboring coastal zone. These negative effects associated with strong natural hypoxia events could have important consequences for the productivity and ecosystem functioning of the coastal zone of the Humboldt Current System if, as suggested by several models, winds favorable to upwelling should increase due to climate change. The effects of natural hypoxia in this coastal zone can be dramatic especially for pelagic and benthic species not adapted to endure conditions of low dissolved oxygen. PMID:28715447

Bathymetric analysis of in-water upwelling-radiance data

NASA Astrophysics Data System (ADS)

Fay, Temple H.; Miller, H. V.; Clark, R. K.

1990-09-01

In June 1988, the Naval Ocean Research and Development Activity (NORDA) collected some "in-water" data using its Towed Underwater Pumping System (TUPS) in the near-shore waters off St. Andrews State Park, Shell Island, Florida. These in situ data include latitude; longitude; depth in meters; narrow-band upwelling at 465 nm, 507 nm, and 532 nm; broad-band downwelling collected at the surface; temperature; salinity; atid transmissivity. In this paper, we investigate the relationship between depth and the normalized upwelling irradiance (upwelling divided by downwelling) in the three bands. Algorithms used to calculate water depth from remotely sensed airborne and satellite multispectral data are applied to the TUPS data and results compared. The TEJPS data have the advantage over most aircraft- and satellite-collected data because they were collected over an essentially uniform bottom type (smooth sandy bottom with steady slope) and have no atmospheric contamination. A new algorithm for depth calculation is proposed.

Experimental investigation of the hydrodynamics in pockmarks using particle tracking velocimetry

NASA Astrophysics Data System (ADS)

Pau, Mauro; Gisler, Galen; Hammer, Øyvind

2014-02-01

Water tank experiments were performed in order to investigate the behaviour of currents in pockmarks. A particle-seeded flow was visualised and quantified with the aid of the particle tracking velocimetry technique. The employed analogue pockmark is a 1:100 idealised scale model of a natural pockmark, while the highest Reynolds number in the experiments was one order of magnitude smaller than in nature. Interaction of the flow with the pockmark geometry resulted in an upwelling current downstream of the pockmark centre, along with enhanced water turbulence in the depression. Scaling-up the experimental measurements, it is found that the upwelling would be capable of preventing the settling of particles as large as very fine sand. Furthermore, the increased turbulence would support the suspended fine material, which can thus be transported away before settling. The net effect for a variable-direction near-bed current over long periods of time would be to winnow the settling sediments and reduce the sedimentation rate in pockmarks. These mechanisms may be responsible for the observed lack of sediment infill and the typical presence of relatively coarser sediments inside pockmarks compared to the surrounding bed. In contrast, sediments transported as bedload are likely to be deposited in pockmarks because of the weakening of near-bed currents as well as lateral flow convergence associated with the upwelling. Bedload, however, may not be the dominant mode of sediment transport in areas covered by cohesive sediments, where pockmarks are found.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Whitledge, T E

The regeneration of nitrogen is an important process that increases the efficiency of the upwelling ecosystem by enlarging their spatial scales. Ammonium regeneration was considered to contribute 42 to 72 percent of phytoplankton nitrogen requirements in the northwest Africa, Peru, and Baja California upwelling systems. Zooplankton are responsible for the largest portion of regenerated nitrogen; however, fish and benthic sediments may be nearly as large. Comparisons of the importance of ammonium regeneration in upwelling areas with coastal and open ocean regions indicate that the percentage contributions are similar. Future nutrient regeneration studies are needed to assess the recycling of benthicmore » sediments, microzooplankton, gelatinous zooplankton, demersal fish, bacterioplankton, and mollusks.« less

Progress on upwelling studies in the China seas

NASA Astrophysics Data System (ADS)

Hu, Jianyu; Wang, Xiao Hua

2016-09-01

East Asian marginal seas surrounding China exhibit rich ocean upwelling, mostly in response to the southwesterly summer monsoon. Upwelling in the China seas, namely, the South China Sea, the Taiwan Strait, the East China Sea, the Yellow Sea, and the Bohai Sea, has become increasingly important because the potential changes in the upwelling may have dramatic ecosystem, socioeconomic, and climate impacts. This paper reviews the progress of upwelling studies in the China seas since the year 2000, by presenting the principal characteristics and new understanding of 12 major upwelling regions in the China seas. Upwelling exhibits long-term variability at intraseasonal to multidecadal scales as well as short-term variability frequently caused by tropical cyclones. It is also associated with the El Niño-Southern Oscillation, local environmental variation, and biogeochemical factors. The coastal upwelling around Hainan Island and the upwelling or cold dome northeast of Taiwan Island are specifically highlighted because they have attracted great interest for decades. This paper summarizes upwelling mechanisms in terms of wind, topography, tide, stratification, and background flow, with applications mostly to the China seas. Finally, we propose some topics for future upwelling research, i.e., potential intensification of coastal upwelling under global climate change, downwelling, intrusion of upwelling into coastal embayments, and the influence of upwelling on fishery and biogeochemical processes.

Variability in bacterial community structure during upwelling in the coastal ocean

USGS Publications Warehouse

Kerkhof, L.J.; Voytek, M.A.; Sherrell, Robert M.; Millie, D.; Schofield, O.

1999-01-01

Over the last 30 years, investigations at the community level of marine bacteria and phytoplankton populations suggest they are tightly coupled. However, traditional oceanographic approaches cannot assess whether associations between specific bacteria and phytoplankton exist. Recently, molecular based approaches have been implemented to characterize specific members of different marine bacterial communities. Yet, few molecular-based studies have examined coastal upwelling situations. This is important since upwelling systems provide a unique opportunity for analyzing the association between specific bacteria and specific phytoplankton in the ocean. It is widely believed that upwelling can lead to changes in phytoplankton populations (blooms). Thus, if specific associations exist, we would expect to observe changes in the bacterial population triggered by the bloom. In this paper, we present preliminary data from coastal waters off New Jersey that confirm a shift in bacterial communities during a 1995 upwelling event recorded at a long-term earth observatory (LEO-15) in the Mid-Atlantic Bight. Using PCR amplification and cloning, specific bacterial 16S ribosomal RNA sequences were found which were present in upwelling samples during a phytoplankton bloom, but were not detected in non-bloom samples (surface seawater, offshore sites or sediment samples) collected at the same time or in the same area. These findings are consistent with the notion of specific associations between bacteria and phytoplankton in the ocean. However, further examination of episodic events, such as coastal upwelling, are needed to confirm the existence of specific associations. Additionally, experiments need to be performed to elucidate the mechanisms leading to the specific linkages between a group of bacteria and a group of phytoplankton.

Three-Dimensional Spherical Models of Convection in the Earth's Mantle.

PubMed

Bercovici, D; Schubert, G; Glatzmaier, G A

1989-05-26

Three-dimensional, spherical models of mantle convection in the earth reveal that upwelling cylindrical plumes and downwelling planar sheets are the primary features of mantle circulation. Thus, subduction zones and descending sheetlike slabs in the mantle are fundamental characteristics of thermal convection in a spherical shell and are not merely the consequences of the rigidity of the slabs, which are cooler than the surrounding mantle. Cylindrical mantle plumes that cause hotspots such as Hawaii are probably the only form of active upwelling and are therefore not just secondary convective currents separate from the large-scale mantle circulation. Active sheetlike upwellings that could be associated with mid-ocean ridges did not develop in the model simulations, a result that is in agreement with evidence suggesting that ridges are passive phenomena resulting from the tearing of surface plates by the pull of descending slabs.

Topographic Beta Spiral and Onshore Intrusion of the Kuroshio Current

NASA Astrophysics Data System (ADS)

Yang, De-Zhou; Huang, Rui Xin; Yin, Bao-shu; Feng, Xing-Ru; Chen, Hai-ying; Qi, Ji-Feng; Xu, Ling-jing; Shi, Yun-long; Cui, Xuan; Gao, Guan-Dong; Benthuysen, Jessica A.

2018-01-01

The Kuroshio intrusion plays a vitally important role in carrying nutrients to marginal seas. However, the key mechanism leading to the Kuroshio intrusion remains unclear. In this study we postulate a mechanism: when the Kuroshio runs onto steep topography northeast of Taiwan, the strong inertia gives rise to upwelling over topography, leading to a left-hand spiral in the stratified ocean. This is called the topographic beta spiral, which is a major player regulating the Kuroshio intrusion; this spiral can be inferred from hydrographic surveys. In the world oceans, the topographic beta spirals can be induced by upwelling generated by strong currents running onto steep topography. This is a vital mechanism regulating onshore intruding flow and the cross-shelf transport of energy and nutrients from the Kuroshio Current to the East China Sea. This topographic beta spiral reveals a long-term missing link between the oceanic general circulation theory and shelf dynamic theory.

Seasonal fluctuations of ichthyoplankton assemblage in the northeastern South China Sea influenced by the Kuroshio intrusion

NASA Astrophysics Data System (ADS)

Huang, Delian; Zhang, Xia; Jiang, Zhijian; Zhang, Jingping; Arbi, Iman; Jiang, Xin; Huang, Xiaoping; Zhang, Wenjing

2017-09-01

The distribution and assemblage of ichthyoplankton related to local hydrographic features, especially intrusion of the Kuroshio Current (KC) and Guangdong Coastal Current (GCC) in the northeastern South China Sea (NESCS) were investigated in this study. A total of 193 species of ichthyoplankton belonging to 141 genera and 66 families were recognized in summer 2015 and late-winter 2016. The ichthyoplankton assemblage was identified with distinct seasonal differences, and the differences were responded well with the oceanography conditions. In summer, the assemblages were identified into offshore and inshore groups, as controlled by the South China Sea Warm Current (SCSWC) in off-shelf, upwelling, and the diluted water from the Pearl River in inshore. In winter, three groups were divided, representing the southwestern inshore, intrusion of the KC in the eastern offshore, and the GCC in the northern inshore area, respectively. Furthermore, Sigmops gracilis and Vinciguerria sp.3 were probably brought into the NESCS by intrusion of the KC from the eastern Luzon Strait. In addition, high ichthyoplankton abundance was found in high chlorophyll a located in upwelling areas in the northern coastal area in summer and in the southwestern Taiwan Bank in winter, respectively. The nutrition outcropped by the upwelling together, and those brought from the Pearl River probably supported high food availability of the ichthyoplankton in the northern coast of the NESCS.

The Arabian Sea as a high-nutrient, low-chlorophyll region during the late Southwest Monsoon

NASA Astrophysics Data System (ADS)

Naqvi, S. W. A.; Moffett, J. W.; Gauns, M. U.; Narvekar, P. V.; Pratihary, A. K.; Naik, H.; Shenoy, D. M.; Jayakumar, D. A.; Goepfert, T. J.; Patra, P. K.; Al-Azri, A.; Ahmed, S. I.

2010-07-01

Extensive observations were made during the late Southwest Monsoon of 2004 over the Indian and Omani shelves, and along a transect that extended from the southern coast of Oman to the central west coast of India, tracking the southern leg of the US JGOFS expedition (1994-1995) in the west. The data are used, in conjunction with satellite-derived data, to investigate long-term trends in chlorophyll and sea surface temperature, indicators of upwelling intensity, and to understand factors that control primary production (PP) in the Arabian Sea, focussing on the role of iron. Our results do not support an intensification of upwelling in the western Arabian Sea, reported to have been caused by the decline in the winter/spring Eurasian snow cover since 1997. We also noticed, for the first time, an unexpected development of high-nutrient, low-chlorophyll condition off the southern Omani coast. This feature, coupled with other characteristics of the system, such as a narrow shelf and relatively low iron concentrations in surface waters, suggest a close similarity between the Omani upwelling system and the Peruvian and California upwelling systems, where PP is limited by iron. Iron limitation of PP may complicate simple relationship between upwelling and PP assumed by previous workers, and contribute to the anomalous offshore occurrence of the most severe oxygen (O2) depletion in the region. Over the much wider Indian shelf, which experiences large-scale bottom water O2-depletion in summer, adequate iron supply from reducing bottom-waters and sediments seems to support moderately high PP; however, such production is restricted to the thin, oxygenated surface layer, probably because of the unsuitability of the O2-depleted environment for the growth of oxygenic photosynthesizers.

Phytoplankton biomass and microbial abundances during the spring upwelling season in the coastal area off Concepción, central-southern Chile: Variability around a time series station

NASA Astrophysics Data System (ADS)

Morales, Carmen E.; Anabalón, Valeria

2012-01-01

In the coastal system off Concepción, time series observations at a fixed station (St. 18) have shown strong seasonal changes in the oceanographic environment of the upper layer (<35 m depth), accompanied by large increases in phytoplankton biomass during the spring-summer upwelling season. These blooms, dominated by microplanktonic diatoms, have usually overshadowed the relevance of the smaller microbial components during upwelling. This study focuses on the variability of oceanographic conditions and their association with the structure of the planktonic community (size fractionated chlorophyll-a and microbial abundances) in the upper layer during the upwelling season, examining the extent to which St. 18 is representative of the coastal system off Concepción during springtime. For this purpose, data from three consecutive springs (2004, 2005, 2006) were compared, which included cruises for all years (8 stations around St. 18) as well as monthly sampling at St. 18. Most of the spatial (submesoscale) variability in chlorophyll-a and the microbial components was not significant, but data dispersion around mean values was high. Water column structure (temperature and salinity) in the upper layer explained a significant fraction (25-65%) of the spatial variability in most of the planktonic components; their responses to oceanographic variability were linear in some cases and non-linear in others. For the most part, St. 18 appears to adequately represent mean oceanographic conditions and the structure of planktonic communities in the coastal waters off Concepción during springtime, however spatial variability needs to be taken into account in the interpretations of temporal changes at this fixed station as well as in assessments of carbon flow within, and exportation processes from, this upwelling system.

A wind-driven, hybrid latent and sensible heat coastal polynya off Barrow, Alaska

NASA Astrophysics Data System (ADS)

Hirano, Daisuke; Fukamachi, Yasushi; Watanabe, Eiji; Ohshima, Kay I.; Iwamoto, Katsushi; Mahoney, Andrew R.; Eicken, Hajo; Simizu, Daisuke; Tamura, Takeshi

2016-01-01

The nature of the Barrow Coastal Polynya (BCP), which forms episodically off the Alaska coast in winter, is examined using mooring data, atmospheric reanalysis data, and satellite-derived sea-ice concentration and production data. We focus on oceanographic conditions such as water mass distribution and ocean current structure beneath the BCP. Two moorings were deployed off Barrow, Alaska in the northeastern Chukchi Sea from August 2009 to July 2010. For sea-ice season from December to May, a characteristic sequence of five events associated with the BCP has been identified; (1) dominant northeasterly wind parallel to the Barrow Canyon, with an offshore component off Barrow, (2) high sea-ice production, (3) upwelling of warm and saline Atlantic Water beneath the BCP, (4) strong up-canyon shear flow associated with displaced density surfaces due to the upwelling, and (5) sudden suppression of ice growth. A baroclinic current structure, established after the upwelling, caused enhanced vertical shear and corresponding vertical mixing. The mixing event and open water formation occurred simultaneously, once sea-ice production had stopped. Thus, mixing events accompanied by ocean heat flux from the upwelled warm water into the surface layer played an important role in formation/maintenance of the open water area (i.e., sensible heat polynya). The transition from a latent to a sensible heat polynya is well reproduced by a high-resolution pan-Arctic ice-ocean model. We propose that the BCP, previously considered to be a latent heat polynya, is a wind-driven hybrid latent and sensible heat polynya, with both features caused by the same northeasterly wind.

Ichthyoplankton transport from the African coast to the Canary Islands

NASA Astrophysics Data System (ADS)

Brochier, Timothée; Mason, Evan; Moyano, Marta; Berraho, Amina; Colas, Francois; Sangrà, Pablo; Hernández-León, Santiago; Ettahiri, Omar; Lett, Christophe

2011-08-01

The Canary Upwelling System (CUS), a major eastern boundary upwelling system, sustains large cross-border fisheries of small pelagic fish, which poses the question of stock connectivity. Studies suggest that ichthyoplankton transport from the northwest African coast to the Canary Islands (CI) is facilitated by coastal-upwelling associated filaments. Here we analyze connections between larval supply to the CI and sardine and anchovy populations that spawn over the continental shelf. For both species, ichthyoplankton observations (1) at the shelf and (2) near the island of Gran Canaria (GC) are used. Predictions of ichthyoplankton transport to GC are obtained from the Ichthyop Lagrangian transport model, which is forced by a high-resolution hydrodynamic model (ROMS) that reproduces the regional circulation. Results show that upwelling filaments play an important role in the transport of larvae to GC. However, (1) filaments are not the only mechanism, and (2) filament presence does not necessarily imply larval transport. Anchovy and sardine larval presence at GC appears to be independent of the respective adult spawning seasonality. Combining of observed and modeled data does not succeed in reproducing the observed larval patterns at GC. Various hypotheses are proposed to explain this discrepancy in larval transport to GC.

Dynamic of aragonite saturation horizon in waters of Baja California, Mexico

NASA Astrophysics Data System (ADS)

Valencia Gasti, J. A.; Oliva, N. L.; Martin Hernandez-Ayon, J. M.; Durazo, R.; Santamaria-del-Angel, E.; Alin, S. R.; Feely, R. A.

2016-02-01

The status of the ocean acidification can be estimated by hydrographic calibrated data with carbon system variables. Recently empirical models for the coast of southern California and northern Baja California were developed. These models can be applied mainly in places where hydrographic data exist but also with measurements of the carbon system available for calibrations. The aim of this study was to analyze the hydrographic data of a transect in front of Ensenada's coast, corresponding to the line 100 of IMECOCAL's program during the period 1998-2014. Such data was used to apply an empirical model to estimate the aragonite saturation state (Ωa) in order to identify oceanographic conditions that could influence the variability of the depth of saturation horizon that might be in the last 17 years in habitats of shellfish and oyster production areas adjacent to the coast of Ensenada. It was found that the temperature, salinity, oxygen, pH, dissolved inorganic carbon and Ωa showed a seasonal variation with different oceanographic scenarios: (a) during spring-summer the California Current flow to the Ecuador and upwelling events are presented; (b) in autumn-winter the influence the Southern California Bight Eddy can transport water from the subarctic to Ecuador in the oceanic portion of the transect and towards the pole at the coastal side. These oceanographic characteristics encourage that coastal stations present seasonal variability, reflected in the depth of the horizon Ωa shallower ( 66m + 21m) in spring and deeper into the winter ( 122m + 35). It has been reported that the upwelling off the coast of BC transport water from a depth between 80 and 90m in spring and summer; therefore under saturated water (Ωa <1) may be transported to the platform upwelling off the coast of BC

Who’s on top? SST proxy comparison from the Peru Margin Upwelling System

NASA Astrophysics Data System (ADS)

Chazen, C.; Herbert, T.; Altabet, M. A.

2009-12-01

The Peru Margin upwelling region is situated at the interface between the poleward Peru Undercurrent and the equatorward Peru Coastal current. Strong coastal winds force cold, nutrient-rich thermocline waters to the surface. Sea surface temperatures in this region fluctuate sub-annually with changes in the position of the Intertropical convergence zone (ITCZ) and sub-decadally with modifications in the strength of Walker Circulation. In contrast, the temperature of the Peru Margin thermocline is stable, isolated from surface winds and slow to respond to major perturbations in surface temperature. Using high resolution sampling (6-7 year) across an annually laminated sediment core from the heart of the Peru Margin upwelling system (15°S) we explore how Uk’37 temperatures compare with TEX86 temperatures across a 200-year interval in the Mid-late Holocene. Mean late Holocene Uk’37 temperatures, extracted from a high sedimentation rate core from the Peru Margin are similar to modern mean annual sea surface temperatures at 15°S. Multi-decadal-scale (50-100 year) Uk’37 temperature fluctuations oscillate about the mean by 1.5°C. These rapid temperature changes are coherent with fluctuations in surface productivity (C37total and Biogenic Silica) in addition to sub-surface denitrification (δ15N). In contrast, TEX86 temperatures derived from identical samples exhibit colder temperatures than modern mean annual conditions and virtually no temperature fluctuation. We posit that TEX86 values are recording temperatures below the photic zone near the mix-layer-thermocline boundary and may, on longer timescales provide invaluable information about thermocline temperature. With this interpretation in mind, we present a TEX86-based long-term thermocline reconstruction over the Holocene.

Nutrient flux estimates in a tidal basin: A case study of Magdalena lagoon, Mexican Pacific coast

NASA Astrophysics Data System (ADS)

Zaytsev, Oleg; Cervantes-Duarte, Rafael

2018-07-01

Bahia Magdalena (BM), known for its high primary productivity, is one of the largest tidal lagoons on the Mexican Pacific coast of the Baja California Peninsula. BM is located in an area of active coastal upwelling and significant tides with a maximum range of about 2.4 m. Dissolved inorganic nutrients upwelled from the depths are transported by tidal water exchange into the lagoon, contributing to its fertilisation. To estimate the magnitude and mechanisms driving the tidal exchange of water and nutrients, field observations of the nutrient content were made in the inlet area and on the adjacent shelf during March 2003, December 2004 and June, August and November 2005. In March 2003, the research vessel El Puma carried out a complete hydrological study of the area using Seabird-19 CTD profiler. At the same time, a current meter with a tide gauge was installed in the BM inlet, and multiple measurements of currents were made on a section across the inlet with a SonTek hull-mounted Acoustic Doppler Current Profiler (ADCP). Field studies were complemented by numerical experiments with the hydrodynamic model ECOM 3D. Analysis of the currents in the inlet area, deriving from both the ADCP data and the numerical simulation, indicates that the water volume transported during a semidiurnal tidal cycle through the inlet varied from 0.3 km3 for neap tide to 0.82 km3 for spring tide. Net nitrate mass intakes to the lagoon deriving from currents in the mouth can be estimated as 7.0 × 103 kg for neap tides and 20.0 × 103 kg for spring tides, and the maximum phosphate contribution was estimated at 2.5 × 103 kg and 8.5 × 103 kg, respectively. Taking into account that fluvial contribution in the lagoon is practically absent, unexpanded mangroves are distributed mainly at its northern part, and organic sediment decomposition is potentially evaluated as low, we can thus conclude that the coupled effect of upwelling and tidal currents play an important role in fertilising the BM. Naturally, this mechanism works only in periods of upwelling activity, namely, from March to June, and to a lesser extent from September to October.

Steady as He Goes: At-Sea Movement of Adult Male Australian Sea Lions in a Dynamic Marine Environment

PubMed Central

Lowther, Andrew D.; Harcourt, Robert G.; Page, Bradley; Goldsworthy, Simon D.

2013-01-01

The southern coastline of Australia forms part of the worlds' only northern boundary current system. The Bonney Upwelling occurs every austral summer along the south-eastern South Australian coastline, a region that hosts over 80% of the worlds population of an endangered endemic otariid, the Australian sea lion. We present the first data on the movement characteristics and foraging behaviour of adult male Australian sea lions across their South Australian range. Synthesizing telemetric, oceanographic and isotopic datasets collected from seven individuals enabled us to characterise individual foraging behaviour over an approximate two year time period. Data suggested seasonal variability in stable carbon and nitrogen isotopes that could not be otherwise explained by changes in animal movement patterns. Similarly, animals did not change their foraging patterns despite fine-scale spatial and temporal variability of the upwelling event. Individual males tended to return to the same colony at which they were tagged and utilized the same at-sea regions for foraging irrespective of oceanographic conditions or time of year. Our study contrasts current general assumptions that male otariid life history strategies should result in greater dispersal, with adult male Australian sea lions displaying central place foraging behaviour similar to males of other otariid species in the region. PMID:24086338

Atmosphere-ocean feedbacks in a coastal upwelling system

NASA Astrophysics Data System (ADS)

Alves, J. M. R.; Peliz, A.; Caldeira, R. M. A.; Miranda, P. M. A.

2018-03-01

The COAWST (Coupled Ocean-Atmosphere-Wave-Sediment Transport) modelling system is used in different configurations to simulate the Iberian upwelling during the 2012 summer, aiming to assess the atmosphere-ocean feedbacks in the upwelling dynamics. When model results are compared with satellite measurements and in-situ data, two-way coupling is found to have a moderate impact in data-model statistics. A significant reinforcement of atmosphere-ocean coupling coefficients is, however, observed in the two-way coupled run, and in the WRF and ROMS runs forced by previously simulated SST and wind fields, respectively. The increasing in the coupling coefficient is associated with slight, but potentially important changes in the low-level coastal jet in the atmospheric marine boundary layer. While these results do not imply the need for fully coupled simulations in many applications, they show that in seasonal numerical studies such simulations do not degrade the overall model performance, and contribute to produce better dynamical fields.

Atmospheric Wind Relaxations and the Oceanic Response in the California Current Large Marine Ecosystem

NASA Astrophysics Data System (ADS)

Fewings, M. R.; Dorman, C. E.; Washburn, L.; Liu, W.

2010-12-01

On the West Coast of North America in summer, episodic relaxation of the upwelling-favorable winds causes warm water to propagate northward from southern to central California, against the prevailing currents [Harms and Winant 1998, Winant et al. 2003, Melton et al. 2009]. Similar wind relaxations are an important characteristic of coastal upwelling ecosystems worldwide. Although these wind relaxations have an important influence on coastal ocean dynamics, no description exists of the regional atmospheric patterns that lead to wind relaxations in southern California, or of the regional ocean response. We use QuikSCAT wind stress, North American Regional Reanalysis atmospheric pressure products, water temperature and velocity from coastal ocean moorings, surface ocean currents from high-frequency radars, and MODIS satellite sea-surface temperature and ocean color images to analyze wind relaxation events and the ocean response. We identify the events based on an empirical index calculated from NDBC buoy winds [Melton et al. 2009]. We describe the regional evolution of the atmosphere from the Gulf of Alaska to Baja California over the few days leading up to wind relaxations, and the coastal ocean temperature, color, and current response off southern and central California. We analyze ~100 wind relaxation events in June-September during the QuikSCAT mission, 1999-2009. Our results indicate south-central California wind relaxations in summer are tied to mid-level atmospheric low-pressure systems that form in the Gulf of Alaska and propagate southeastward over 3-5 days. As the low-pressure systems reach southern California, the atmospheric pressure gradient along the coast weakens, causing the surface wind stress to relax to near zero. The weak wind signal appears first at San Diego and propagates northward. QuikSCAT data indicate the relaxed winds extend over the entire Southern California Bight and up to 200 km offshore of central California. Atmospheric dynamics in the Gulf of Alaska influence ocean conditions in central and southern California via these wind relaxations. The ocean response within a few km of the coast involves poleward-flowing currents that transport warm water out of the lees of capes and headlands and counter to the direction of the California Current [Send et al. 1987, Harms and Winant 1998, Winant et al. 2003, Melton et al. 2009]. A similar response occurs in the Benguela and Canary Current coastal upwelling systems. The ocean response involves both barotropic and baroclinic dynamics and is consistent with existing geophysical models of buoyant, coastally-trapped plumes [Washburn et al., in prep]. Our ongoing work includes i) studying the regional ocean response to determine its spatial extent, time evolution, and ocean-atmosphere coupling dynamics; ii) developing an atmospheric index to predict wind relaxations in southern California based on pressure in the Gulf of Alaska; iii) examining the strength and frequency of wind relaxations over the past 30 years for connections to El Niño and the Pacific Decadal Oscillation; and iv) predicting future variations in wind relaxations and the response of the California Current Large Marine Ecosystem.

Oceanographic and climatic evolution of the southeastern subtropical Atlantic over the last 3.5 Ma

NASA Astrophysics Data System (ADS)

Petrick, Benjamin; McClymont, Erin L.; Littler, Kate; Rosell-Melé, Antoni; Clarkson, Matthew O.; Maslin, Mark; Röhl, Ursula; Shevenell, Amelia E.; Pancost, Richard D.

2018-06-01

The southeast Atlantic Ocean is dominated by two major oceanic systems: the Benguela Upwelling System, one of the world's most productive coastal upwelling cells and the Agulhas Leakage, which is important for transferring warm salty water from the Indian Ocean to the Atlantic Ocean. Here, we present a multi-proxy record of marine sediments from ODP Site 1087. We reconstruct sea surface temperatures (U37K‧ and TEX86 indices), marine primary productivity (total chlorin and alkenone mass accumulation rates), and terrestrial inputs derived from southern Africa (Ti/Al and Ca/Ti via XRF scanning) to understand the evolution of the Southeast Atlantic Ocean since the late Pliocene. In the late Pliocene and early Pleistocene, ODP Site 1087 was situated within the Benguela Upwelling System, which was displaced southwards relative to present. We recognize a series of events in the proxy records at 3.3, 3.0, 2.2, 1.5, 0.9 and 0.6 Ma, which are interpreted to reflect a combination of changes in the location of major global wind and oceanic systems and local variations in the strength and/or position of the winds, which influence nutrient availability. Although there is a temporary SST cooling observed around the initiation of Northern Hemisphere glaciation (iNHG), proxy records from ODP Site 1087 show no clear climatic transition around 2.7 Ma but instead most of the changes occur before this time. This observation is significant because it has been previously suggested that there should be a change in the location and/or strength of upwelling associated with this climate transition. Rather, the main shifts at ODP Site 1087 occur at ca. 0.9 Ma and 0.6 Ma, associated with the early mid-Pleistocene transition (EMPT), with a clear loss of the previous upwelling-dominated regime. This observation raises the possibility that reorganisation of southeast Atlantic Ocean circulation towards modern conditions was tightly linked to the EMPT, but not to earlier climate transitions.

Three-dimensional spherical models of convection in the earth's mantle

NASA Technical Reports Server (NTRS)

Bercovici, Dave; Schubert, Gerald; Glatzmaier, Gary A.

1989-01-01

Three-dimensional spherical models of mantle convection in the earth reveal that upwelling cylindrical plumes and downwelling planar sheets are the primary features of mantle circulation. Thus subduction zones and descending sheetlike slabs in the mantle are fundamental characteristics of thermal convection in a spherical shell and are not merely the consequences of the rigidity of the slabs, which are cooler than the surrounding mantle. Cylindrical mantle plumes that cause hot spots such as Hawaii are probably the only form of active upwelling and are therefore not just secondary convective currents separate from the large-scale mantle circulation.

Temporal variability and phylogenetic characterization of planktonic anammox bacteria in the coastal upwelling ecosystem off central Chile

NASA Astrophysics Data System (ADS)

Galán, Alexander; Molina, Verónica; Belmar, Lucy; Ulloa, Osvaldo

2012-01-01

The phylogenetic affiliation and temporal variability in the abundance of planktonic anammox bacteria were studied at a time-series station above the continental shelf off central Chile (∼36°S; bottom depth 93 m), a wind-driven, seasonal upwelling area, between August 2006 and April 2008. The study was carried out by cloning and sequencing the 16S rRNA gene and by using catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH). Our results showed the presence of a single anammox bacteria-like ribotype during both upwelling and non-upwelling seasons, which was phylogenetically associated with a recently described oxygen-minimum-zone subcluster within the Candidatus Scalindua clade. Moreover, clear differences were observed in the temporal and vertical distribution of anammox cells. During the upwelling season (austral spring-summer), relatively high abundances (∼5500 cells mL -1) and large cells (0.8 μm 3-75.7 fg C cell -1) were found below 20 m depth. In contrast, during the non-upwelling season (austral fall-winter), lower abundances (∼600 cells mL -1) and smaller cells (0.1 μm 3-22.8 fg C cell -1) were found, predominantly associated with the bottom layer. Overall, our results indicate that the abundance and vertical distribution of anammox planktonic assemblages are related to the occurrence of seasonal, wind-driven, coastal upwelling, which in turn appears to offer favorable conditions for the development of these microorganisms. The dominance of a unique anammox bacteria-like ribotype could be related to the high environmental variability observed in the system, which prevents the establishment of other anammox lineages.

Seasonal and annual variability of coastal sulphur plumes in the northern Benguela upwelling system.

PubMed

Ohde, Thomas; Dadou, Isabelle

2018-01-01

We investigated the seasonal and annual variability of surface sulphur plumes in the northern Benguela upwelling system off Namibia because of their significant impacts on the marine ecosystem, fishing industry, aquaculture farming and tourism due to their toxic properties. We identified the sulphur plumes in ocean colour satellite data of the medium resolution imaging spectrometer (MERIS) for the 2002-2012 time period using the differences in the spectral properties of Namibian Benguela optical water types. The sulphur events have a strong seasonal cycle with pronounced main and off-seasons forced by local and remote-driven processes. The main peak season is in late austral summer and early austral autumn at the beginning of the annual upwelling cycle caused by increasing equatorwards alongshore winds. The sulphur plume activity is high between February and April during the seasonal oxygen minimum associated with the seasonal reduction of cross-shore ventilation of the bottom waters, the seasonal southernmost position of the Angola Benguela Frontal Zone, the seasonal maximum of water mass fractions of South Atlantic and Angola Gyre Central Waters as well as the seasonal arrival of the downwelling coastal trapped waves. The off-season is in austral spring and early austral summer during increased upwelling intensity and enhanced oxygen supply. The annual variability of sulphur events is characterized by very high activities in years 2004, 2005 and 2010 interrupted by periods of lower activity in years 2002 to 2003, 2006 to 2009 and 2011 to 2012. This result can be explained by the relative contributions or adding effects of local and remote-driven forces (from the equatorial area). The probability for the occurrence of sulphur plumes is enhanced in years with a lower annual mean of upwelling intensity, decreased oxygen supply associated with decreased lateral ventilation of bottom waters, more southern position of the Angola Benguela Frontal Zone, increased mass fraction of South Atlantic Central Water and stronger downwelling coastal trapped waves. Understanding of the variability and forcing processes of the toxic sulphur events will help in the future to monitor and forecast them as well as to manage their social and economic consequences in the northern Benguela upwelling system off Namibia.

Oligocene to Holocene sediment drifts and bottom currents on the slope of Gabon continental margin (west Africa). Consequences for sedimentation and southeast Atlantic upwelling

NASA Astrophysics Data System (ADS)

Séranne, Michel; Nzé Abeigne, César-Rostand

1999-10-01

Seismic reflection profiles on the slope of the south Gabon continental margin display furrows 2 km wide and some 200 m deep, that develop normal to the margin in 500-1500 m water depth. Furrows are characterised by an aggradation/progradation pattern which leads to margin-parallel, northwestward migration of their axes through time. These structures, previously interpreted as turbidity current channels, display the distinctive seismic image and internal organisation of sediment drifts, constructed by the activity of bottom currents. Sediment drifts were initiated above a major Oligocene unconformity, and they developed within a Oligocene to Present megasequence of general progradation of the margin, whilst they are markedly absent from the underlying Late Cretaceous-Eocene aggradation megasequence. The presence of upslope migrating sediment waves, and the northwest migration of the sediment drifts indicate deposition by bottom current flowing upslope, under the influence of the Coriolis force. Such landwards-directed bottom currents on the slope probably represent coastal upwelling, which has been active along the west Africa margin throughout the Neogene.

Simulation of Lake Victoria Circulation Patterns Using the Regional Ocean Modeling System (ROMS).

PubMed

Nyamweya, Chrispine; Desjardins, Christopher; Sigurdsson, Sven; Tomasson, Tumi; Taabu-Munyaho, Anthony; Sitoki, Lewis; Stefansson, Gunnar

2016-01-01

Lake Victoria provides important ecosystem services including transport, water for domestic and industrial uses and fisheries to about 33 million inhabitants in three East African countries. The lake plays an important role in modulating regional climate. Its thermodynamics and hydrodynamics are also influenced by prevailing climatic and weather conditions on diel, seasonal and annual scales. However, information on water temperature and circulation in the lake is limited in space and time. We use a Regional Oceanographic Model System (ROMS) to simulate these processes from 1st January 2000 to 31st December 2014. The model is based on real bathymetry, river runoff and atmospheric forcing data using the bulk flux algorithm. Simulations show that the water column exhibits annual cycles of thermo-stratification (September-May) and mixing (June-August). Surface water currents take different patterns ranging from a lake-wide northward flow to gyres that vary in size and number. An under flow exists that leads to the formation of upwelling and downwelling regions. Current velocities are highest at the center of the lake and on the western inshore waters indicating enhanced water circulation in those areas. However, there is little exchange of water between the major gulfs (especially Nyanza) and the open lake, a factor that could be responsible for the different water quality reported in those regions. Findings of the present study enhance understanding of the physical processes (temperature and currents) that have an effect on diel, seasonal, and annual variations in stratification, vertical mixing, inshore-offshore exchanges and fluxes of nutrients that ultimately influence the biotic distribution and trophic structure. For instance information on areas/timing of upwelling and vertical mixing obtained from this study will help predict locations/seasons of high primary production and ultimately fisheries productivity in Lake Victoria.

Bio-optical signatures and biogeochemistry from intense upwelling and relaxation in coastal California

NASA Astrophysics Data System (ADS)

Kudela, Raphael M.; Garfield, Newell; Bruland, Kenneth W.

2006-12-01

The NSF-sponsored Coastal Ocean Processes Wind Events and Shelf Transport (WEST) experiment investigates the interplay between wind-driven transport and shelf productivity; while eastern boundary shelves are characterized by high productivity due to upward fluxes of nutrients into the euphotic zone, wind forcing also represents negative physical and biological controls via offshore transport and deep (light-limiting) mixing of primary producers. Although this interaction has been well documented for eastern boundary systems generally and for California specifically, one of the primary goals of WEST was to characterize more fully the interplay between positive and negative effects of wind stress, which result in the consistently elevated biological productivity in these shelf regions. During 3 month-long summer cruises (2000-2002) we observed extremes in upwelling/relaxation, using both in situ instrumentation and remotely sensed data. Relationships between optical and physical properties were examined, with emphasis on biogeochemical implications. During 2000, the WEST region was optically dominated by phytoplankton and covarying constituents. During 2001 and 2002, periods of more intense upwelling favorable winds, we observed a transition to optical properties dominated by detrital and inorganic materials. In all years, the continental shelf break provided a natural boundary between optically distinct shelf and open ocean waters. During 2002, we obtained discrete trace-metal measurements of particulate iron and aluminum; we develop a bio-optical proxy for acetic-acid leachable iron from backscatter and fluorescence, and demonstrate that particulate iron is not well correlated to traditional upwelling proxies such as macronutrients, temperature, and salinity. We conclude that the shelf break between ca. 100 and 200 m water depth serves as a natural break point between coastal and oceanic water masses in this region, and that the elevated biomass and productivity associated with this eastern boundary current regime is dominated by these iron rich, shallow shelf waters.

Air-Sea Interaction in the Somali Current Region

NASA Astrophysics Data System (ADS)

Jensen, T. G.; Rydbeck, A.

2017-12-01

The western Indian Ocean is an area of high eddy-kinetic energy generated by local wind-stress curl, instability of boundary currents as well as Rossby waves from the west coast of India and the equatorial wave guide as they reflect off the African coast. The presence of meso-scale eddies and coastal upwelling during the Southwest Monsoon affects the air-sea interaction on those scales. The U.S. Navy's Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS) is used to understand and quantify the surface flux, effects on surface waves and the role of Sea Surface Temperature anomalies on ocean-atmosphere coupling in that area. The COAMPS atmosphere model component with 9 km resolution is fully coupled to the Navy Coastal Ocean Model (NCOM) with 3.5 km resolution and the Simulating WAves Nearshore (SWAN) wave model with 10 km resolution. Data assimilation using a 3D-variational approach is included in hindcast runs performed daily since June 1, 2015. An interesting result is that a westward jet associated with downwelling equatorial Rossy waves initiated the reversal from the southward Somali Current found during the northeast monsoon to a northward flow in March 2016 more than a month before the beginning of the southwest monsoon. It is also found that warm SST anomalies in the Somali Current eddies, locally increase surface wind speed due to an increase in the atmospheric boundary layer height. This results in an increase in significant wave height and also an increase in heat flux to the atmosphere. Cold SST anomalies over upwelling filaments have the opposite impacts on air-sea fluxes.

Hydrographic characterization of southeast Arabian Sea during the wane of southwest monsoon and spring intermonsoon.

PubMed

Vimal Kumar, K G; Dinesh Kumar, P K; Smitha, B R; Habeeb Rahman, H; Josia, Jacob; Muraleedharan, K R; Sanjeevan, V N; Achuthankutty, C T

2008-05-01

Seasonal variation of the hydrography along the southeast Arabian Sea is described using data collected onboard FORV Sagar Sampada in September--October 2003 (later phase of Southwest monsoon, SWM) and March--April 2004 (Spring inter monsoon, SIM). During the later phase of the SWM, upwelling was in the withdrawal phase and the frontal structure was clearer in the northern sections (13 and 15 degrees N lat) indicating strong upwelling in the area. The driving force of upwelling is identified as the combination of alongshore wind stress and remote forcing with a latitudinal variability. Although a more prominent upwelling was found in the north, a maximum surface Chlorophyll-a was found in the south (10 degrees N). During the SIM, the area was characterized by oligotrophic water with relatively high Sea Surface Temperature (>29 degrees C) and low salinity (33.8 to 35.4). During March, the surface hydrography was found to be controlled mainly by the intrusion of low-saline waters from the south, while during September by the high saline water from the north. The presence of various water masses [Arabian Sea High Salinity Water (ASHSW), Persian Gulf Water (PGW), Red Sea Water (RSW)] and their seasonal variations in the region is discussed and their decreasing influence towards the south is noted during both periods of observation. During the SWM, the dynamic topography showed the equator-ward flow of the West India Coastal Current (WICC) at the surface and a pole-ward coastal under current at sub-thermocline depth. During the SIM, surface circulation revealed the WICC flowing pole-ward north of 13 degrees N, but equator-ward flow in the south, with a clockwise circulation around the Lakshadweep High.

The deep Canary poleward undercurrent

NASA Astrophysics Data System (ADS)

Velez-Belchi, P. J.; Hernandez-Guerra, A.; González-Pola, C.; Fraile, E.; Collins, C. A.; Machín, F.

2012-12-01

Poleward undercurrents are well known features in Eastern Boundary systems. In the California upwelling system (CalCEBS), the deep poleward flow has been observed along the entire outer continental shelf and upper-slope, using indirect methods based on geostrophic estimates and also using direct current measurements. The importance of the poleward undercurrents in the CalCEBS, among others, is to maintain its high productivity by means of the transport of equatorial Pacific waters all the way northward to Vancouver Island and the subpolar gyre but there is also concern about the low oxygen concentration of these waters. However, in the case of the Canary Current Eastern Boundary upwelling system (CanCEBS), there are very few observations of the poleward undercurrent. Most of these observations are short-term mooring records, or drifter trajectories of the upper-slope flow. Hence, the importance of the subsurface poleward flow in the CanCEBS has been only hypothesized. Moreover, due to the large differences between the shape of the coastline and topography between the California and the Canary Current system, the results obtained for the CalCEBS are not completely applicable to the CanCEBS. In this study we report the first direct observations of the continuity of the deep poleward flow of the Canary Deep Poleward undercurrent (CdPU) in the North-Africa sector of the CanCEBS, and one of the few direct observations in the North-Africa sector of the Canary Current eastern boundary. The results indicate that the Canary Island archipelago disrupts the deep poleward undercurrent even at depths where the flow is not blocked by the bathymetry. The deep poleward undercurrent flows west around the eastern-most islands and north east of the Conception Bank to rejoin the intermittent branch that follows the African slope in the Lanzarote Passage. This hypothesis is consistent with the AAIW found west of Lanzarote, as far as 17 W. But also, this hypothesis would be coherent with a cyclonic circulation associated with the Savage Islands, the Conception bank and the Canary Islands sub basin that would redistribute the AAIW northeast of the Canaries.

Climate change. Six centuries of variability and extremes in a coupled marine-terrestrial ecosystem.

PubMed

Black, Bryan A; Sydeman, William J; Frank, David C; Griffin, Daniel; Stahle, David W; García-Reyes, Marisol; Rykaczewski, Ryan R; Bograd, Steven J; Peterson, William T

2014-09-19

Reported trends in the mean and variability of coastal upwelling in eastern boundary currents have raised concerns about the future of these highly productive and biodiverse marine ecosystems. However, the instrumental records on which these estimates are based are insufficiently long to determine whether such trends exceed preindustrial limits. In the California Current, a 576-year reconstruction of climate variables associated with winter upwelling indicates that variability increased over the latter 20th century to levels equaled only twice during the past 600 years. This modern trend in variance may be unique, because it appears to be driven by an unprecedented succession of extreme, downwelling-favorable, winter climate conditions that profoundly reduce productivity for marine predators of commercial and conservation interest. Copyright © 2014, American Association for the Advancement of Science.

Analysis of longwave radiation for the Earth-atmosphere system

NASA Technical Reports Server (NTRS)

Tiwari, S. N.; Venuru, C. S.; Subramanian, S. V.

1983-01-01

Accurate radiative transfer models are used to determine the upwelling atmospheric radiance and net radiative flux in the entire longwave spectral range. The validity of the quasi-random band model is established by comparing the results of this model with those of line-by-line formulations and with available theoretical and experimental results. Existing radiative transfer models and computer codes are modified to include various surface and atmospheric effects (surface reflection, nonequilibrium radiation, and cloud effects). The program is used to evaluate the radiative flux in clear atmosphere, provide sensitivity analysis of upwelling radiance in the presence of clouds, and determine the effects of various climatological parameters on the upwelling radiation and anisotropic function. Homogeneous and nonhomogeneous gas emissivities can also be evaluated under different conditions.

Persistent warmth across the Benguela upwelling system during the Pliocene epoch

NASA Astrophysics Data System (ADS)

Rosell-Melé, Antoni; Martínez-Garcia, Alfredo; McClymont, Erin L.

2014-01-01

A feature of Pliocene climate is the occurrence of "permanent El Niño-like" or "El Padre" conditions in the Pacific Ocean. From the analysis of sediment cores in the modern northern Benguela upwelling, we show that the mean oceanographic state off Southwest Africa during the warm Pliocene epoch was also analogous to that of a persistent Benguela "El Niño". At present these events occur when massive southward flows of warm and nutrient-poor waters extend along the coasts of Angola and Namibia, with dramatic effects on regional marine ecosystems and rainfall. We propose that the persistent warmth across the Pliocene in the Benguela upwelling ended synchronously with the narrowing of the Indonesian seaway, and the early intensification of the Northern Hemisphere Glaciations around 3.0-3.5 Ma. The emergence of obliquity-related cycles in the Benguela sea surface temperatures (SST) after 3 Ma highlights the development of strengthened links to high latitude orbital forcing. The subsequent evolution of the Benguela upwelling system was characterized by the progressive intensification of the meridional SST gradients, and the emergence of the 100 ky cycle, until the modern mean conditions were set at the end of the Mid Pleistocene transition, around 0.6 Ma. These findings support the notion that the interplay of changes in the depth of the global thermocline, atmospheric circulation and tectonics preconditioned the climate system for the end of the warm Pliocene epoch and the subsequent intensification of the ice ages.

Differences between mono-generic and mixed diatom silicon isotope compositions trace present and past nutrient utilisation off Peru

NASA Astrophysics Data System (ADS)

Doering, Kristin; Ehlert, Claudia; Grasse, Patricia; Crosta, Xavier; Fleury, Sophie; Frank, Martin; Schneider, Ralph

2016-03-01

In this study we combine for the first time silicon (Si) isotope compositions of small mixed diatom species (δ30SibSiO2) and of large handpicked mono-generic (i.e. genus = Coscinodiscus) diatom samples (δ30SiCoscino) with diatom assemblages extracted from marine sediments in the Peruvian upwelling region in order to constrain present and past silicate utilisation. The extension of a previous core-top data set from the Peruvian shelf demonstrates that δ30SiCoscino values record near-complete Si utilisation, as these are similar to the isotopic composition of the subsurface source waters feeding the upwelling. In contrast, the δ30SibSiO2 of small mixed diatom species increase southward along the shelf as well as towards the shore. We attribute highest δ30SibSiO2 values partly to transient iron limitation but primarily to the gradual increase of Si isotope fractionation within the seasonal diatom succession, which are mainly recorded by small diatom species during intense bloom events. In contrast, lower δ30SibSiO2 values are related to initial Si isotope utilisation during periods of weak upwelling, when low Si(OH)4 concentrations do not permit intense blooms and small diatom species record substantially lower δ30Si signatures. As such, we propose that the intensity of the upwelling can be deduced from the offset between δ30SibSiO2 and δ30SiCoscino (Δ30Sicoscino-bSiO2), which is low for strong upwelling conditions and high for prevailing weak upwelling. We apply the information extracted from surface sediments to generate a record of the present-day main upwelling region covering the past 17,700 years and find that this location has also been characterized by a persistent offset (Δ30Sicoscino-bSiO2). By comparison with the diatom assemblages we show that the coastal upwelling system changed markedly between weak and strong upwelling conditions. In addition, our model calculations to quantify species-specific Si isotope fractionation effects based on the diatom assemblages indicate an overall minor influence that cannot explain the high amplitude in the measured δ30SibSiO2 record.

Contribution of topographically generated submesoscale turbulence to Southern Ocean overturning

NASA Astrophysics Data System (ADS)

Ruan, Xiaozhou; Thompson, Andrew F.; Flexas, Mar M.; Sprintall, Janet

2017-11-01

The ocean's global overturning circulation regulates the transport and storage of heat, carbon and nutrients. Upwelling across the Southern Ocean's Antarctic Circumpolar Current and into the mixed layer, coupled to water mass modification by surface buoyancy forcing, has been highlighted as a key process in the closure of the overturning circulation. Here, using twelve high-resolution hydrographic sections in southern Drake Passage, collected with autonomous ocean gliders, we show that Circumpolar Deep Water originating from the North Atlantic, known as Lower Circumpolar Deep Water, intersects sloping topography in narrow and strong boundary currents. Observations of strong lateral buoyancy gradients, enhanced bottom turbulence, thick bottom mixed layers and modified water masses are consistent with growing evidence that topographically generated submesoscale flows over continental slopes enhance near-bottom mixing, and that cross-density upwelling occurs preferentially over sloping topography. Interactions between narrow frontal currents and topography occur elsewhere along the path of the Antarctic Circumpolar Current, which leads us to propose that such interactions contribute significantly to the closure of the overturning in the Southern Ocean.

Variations of the Organic Matter Composition in the Sea Surface Microlayer: A Comparison between Open Ocean, Coastal, and Upwelling Sites Off the Peruvian Coast

PubMed Central

Zäncker, Birthe; Bracher, Astrid; Röttgers, Rüdiger; Engel, Anja

2017-01-01

The sea surface microlayer (SML) is the thin boundary layer between the ocean and the atmosphere, making it important for air-sea exchange processes. However, little is known about what controls organic matter composition in the SML. In particular, there are only few studies available on the differences of the SML of various oceanic systems. Here, we compared the organic matter and neuston species composition in the SML and the underlying water (ULW) at 11 stations with varying distance from the coast in the Peruvian upwelling regime, a system with high emissions of climate relevant trace gases, such as N2O and CO2. In the open ocean, organic carbon, and amino acids were highly enriched in the SML compared to the ULW. The enrichment decreased at the coastal stations and vanished in the upwelling regime. At the same time, the degradation of organic matter increased from the open ocean to the upwelling stations. This suggests that in the open ocean, upward transport processes or new production of organic matter within the SML are faster than degradation processes. Phytoplankton was generally not enriched in the SML, one group though, the Trichodesmium-like TrL (possibly containing Trichodesmium), were enriched in the open ocean but not in the upwelling region indicating that they find a favorable habitat in the open ocean SML. Our data show that the SML is a distinct habitat; its composition is more similar among different systems than between SML and ULW of a single station. Generally the enrichment of organic matter is assumed to be reduced when encountering low primary production and high wind speeds. However, our study shows the highest enrichments of organic matter in the open ocean which had the lowest primary production and the highest wind speeds. PMID:29375483

Variations of the Organic Matter Composition in the Sea Surface Microlayer: A Comparison between Open Ocean, Coastal, and Upwelling Sites Off the Peruvian Coast.

PubMed

Zäncker, Birthe; Bracher, Astrid; Röttgers, Rüdiger; Engel, Anja

2017-01-01

The sea surface microlayer (SML) is the thin boundary layer between the ocean and the atmosphere, making it important for air-sea exchange processes. However, little is known about what controls organic matter composition in the SML. In particular, there are only few studies available on the differences of the SML of various oceanic systems. Here, we compared the organic matter and neuston species composition in the SML and the underlying water (ULW) at 11 stations with varying distance from the coast in the Peruvian upwelling regime, a system with high emissions of climate relevant trace gases, such as N 2 O and CO 2 . In the open ocean, organic carbon, and amino acids were highly enriched in the SML compared to the ULW. The enrichment decreased at the coastal stations and vanished in the upwelling regime. At the same time, the degradation of organic matter increased from the open ocean to the upwelling stations. This suggests that in the open ocean, upward transport processes or new production of organic matter within the SML are faster than degradation processes. Phytoplankton was generally not enriched in the SML, one group though, the Trichodesmium -like TrL (possibly containing Trichodesmium ), were enriched in the open ocean but not in the upwelling region indicating that they find a favorable habitat in the open ocean SML. Our data show that the SML is a distinct habitat; its composition is more similar among different systems than between SML and ULW of a single station. Generally the enrichment of organic matter is assumed to be reduced when encountering low primary production and high wind speeds. However, our study shows the highest enrichments of organic matter in the open ocean which had the lowest primary production and the highest wind speeds.

Simultaneous Quantification of Temperature, Pyroxenite Abundance, and Upwelling Rates in the Iceland Mantle Source

NASA Astrophysics Data System (ADS)

Brown, E.; Lesher, C. E.

2014-12-01

The compositions and volumes of basalts erupted at the earth's surface are a function of mantle temperature, mantle composition, and the rate at which the mantle upwells through the melting zone. Thus, basaltic magmatism has long been used to probe the thermal and physiochemical state of the earth's mantle. Great insight has been gained into the mantle beneath the global spreading ridge system, where the mantle source is assumed to be homogeneous peridotite that upwells passively [1]. However, it is now recognized that many basalt source regions are lithologically heterogeneous (i.e. containing recycled lithospheric material ranging from harzburgite to pyroxenite) and upwell at rates in excess of those governed by plate separation. To account for these complexities, we have developed a forward melting model for lithologically heterogeneous mantle that incorporates thermodynamically and experimentally constrained melting functions for a range of peridotite and pyroxenite lithologies. The model is unique because it quantifies mantle upwelling rates based on the net buoyancy of the source, thus providing a means for linking basalt compositions/volumes to mantle flow while accounting for source heterogeneity. We apply the model to investigate the mantle properties governing magmatism along different rift segments in Iceland, where lithologic heterogeneity and variable upwelling rates have been inferred through geochemical means [2,3]. Using constraints from seismically determined crustal thicknesses and recent estimates of the proportion of pyroxenite-derived melt contributing to Icelandic basalt compositions [4,5], we show that mantle sources beneath Iceland have excess potential temperatures >85 °C, contain <7% pyroxenite, and maximum upwelling rates ~14 times the passive rate. Our modeling highlights the dominant role of elevated mantle temperature and enhanced upwelling for high productivity magmatism in Iceland, and a subordinate role for mantle heterogeneity, which is required to account for much of the observed chemical and isotopic diversity. [1] Langmuir et al, 1992, AGU Geophys. Mono. Ser. 71 [2] Chauvel & Hemond, 2000, G-cubed, v 1 [3] Kokfelt et al, 2003, EPSL, v 214 [4] Sobolev et al, 2007, Science, v 316 [5] Shorttle et al, 2014, EPSL, v 395

The Effects of Ridge Axis Width on Mantle Melting at Mid-Ocean Ridges

NASA Astrophysics Data System (ADS)

Montesi, L.; Magni, V.; Gaina, C.

2017-12-01

Mantle upwelling in response to plate divergence produces melt at mid-ocean ridges. Melt starts when the solidus is crossed and stops when conductive cooling overcomes heat advection associated with the upwelling. Most mid-ocean ridge models assume that divergence takes place only in a narrow zone that defines the ridge axis, resulting in a single upwelling. However, more complex patterns of divergence are occasionally observed. The rift axis can be 20 km wide at ultraslow spreading center. Overlapping spreading center contain two parallel axes. Rifting in backarc basins is sometimes organized as a series of parallel spreading centers. Distributing plate divergence over several rifts reduces the intensity of upwelling and limits melting. Can this have a significant effect on the expected crustal thickness and on the mode of melt delivery at the seafloor? We address this question by modeling mantle flow and melting underneath two spreading centers separated by a rigid block. We adopt a non-linear rheology that includes dislocation creep, diffusion creep and yielding and include hydrothermal cooling by enhancing thermal conductivity where yielding takes place. The crustal thickness decreases if the rifts are separated by 30 km or more but only if the half spreading rate is between 1 and 2 cm/yr. At melting depth, a single upwelling remains the norm until the separation of the rifts exceeds a critical value ranging from 15 km in the fastest ridges to more than 50 km at ultraslow spreading centers. The stability of the central upwelling is due to hydrothermal cooling, which prevents hot mantle from reaching the surface at each spreading center. When hydrothermal cooling is suppressed, or the spreading centers are sufficiently separated, the rigid block becomes extremely cold and separates two distinct, highly asymmetric upwellings that may focus melt beyond the spreading center. In that case, melt delivery might drive further and further the divergence centers, whereas, when a single upwelling is retained, melt delivery would drive the spreading centers closer together. Thus, the system composed of two rifts is unstable and, if observed in nature, indicates either a transient geodynamic regime, like a recent change in spreading rates, or control structural or stress heterogeneities.

An equilibrium model for the coupled ocean-atmosphere boundary layer in the tropics

NASA Technical Reports Server (NTRS)

Sui, C.-H.; Lau, K.-M.; Betts, Alan K.

1991-01-01

An atmospheric convective boundary layer (CBL) model is coupled to an ocean mixed-layer (OML) model in order to study the equilibrium state of the coupled system in the tropics, particularly in the Pacific region. The equilibrium state of the coupled system is solved as a function of sea-surface temperature (SST) for a given surface wind and as a function of surface wind for a given SST. It is noted that in both cases, the depth of the CBL and OML increases and the upwelling below the OML decreases, corresponding to either increasing SST or increasing surface wind. The coupled ocean-atmosphere model is solved iteratively as a function of surface wind for a fixed upwelling and a fixed OML depth, and it is observed that SST falls with increasing wind in both cases. Realistic gradients of mixed-layer depth and upwelling are observed in experiments with surface wind and SST prescribed as a function of longitude.

Revealing sources and chemical identity of iron ligands across the California Current System

NASA Astrophysics Data System (ADS)

Boiteau, R.; Repeta, D.; Fitzsimmons, J. N.; Parker, C.; Twining, B. S.; Baines, S.

2016-02-01

The California Current System is one of the most productive regions of the ocean, fueled by the upwelling of nutrient rich water. Differences in the supply of micronutrient iron to surface waters along the coast lead to a mosaic of iron-replete and iron-limited conditions across the region, affecting primary production and community composition. Most of the iron in this region is supplied by upwelling of iron from the benthic boundary layer that is complexed by strong organic ligands. However, the source, identity, and bioavailability of these ligands are unknown. Here, we used novel hyphenated chromatography mass spectrometry approaches to structurally characterize organic ligands across the region. With these methods, iron ligands are detected with liquid chromatography coupled to inductively coupled plasma mass spectrometry (LC-ICPMS), and then their mass and fragmentation spectra are determined by high resolution electrospray ionization mass spectrometry (LC-ESIMS). Iron isotopic exchange was used to compare the relative binding strengths of different ligands. Our survey revealed a broad range of ligands from multiple sources. Benthic boundary layers and anoxic sediments were sources of structurally amorphous weak ligands, likely organic degradation products, as well as siderophores, strong iron binding molecules that facilitate iron acquisition. In the euphotic zone, marine microbes and zooplankton grazing produced a wide distribution of other compounds that included known and novel siderophores. This work demonstrates that the chemical nature of ligands from different sources varies substantially and has important implications for iron biogeochemical cycling and availability to members of the microbial community.

Processes influencing seasonal hypoxia in the northern California Current System

PubMed Central

Connolly, T. P.; Hickey, B. M.; Geier, S. L.; Cochlan, W. P.

2010-01-01

This paper delineates the role of physical and biological processes contributing to hypoxia, dissolved oxygen (DO) < 1.4 mL/L, over the continental shelf of Washington State in the northern portion of the California Current System (CCS). In the historical record (1950–1986) during the summer upwelling season, hypoxia is more prevalent and severe off Washington than further south off northern Oregon. Recent data (2003–2005) show that hypoxia over the Washington shelf occurred at levels previously observed in the historical data. 2006 was an exception, with hypoxia covering ~5000 km2 of the Washington continental shelf and DO concentrations below 0.5 mL/L at the inner shelf, lower than any known previous observations at that location. In the four years studied, upwelling of low DO water and changes in source water contribute to interannual variability, but cannot account for seasonal decreases below hypoxic concentrations. Deficits of DO along salinity surfaces, indicating biochemical consumption of DO, vary significantly between surveys, accounting for additional decreases of 0.5–2.5 mL/L by late summer. DO consumption is associated with denitrification, an indicator of biochemical sediment processes. Mass balances of DO and nitrate show that biochemical processes in the water column and sediments each contribute ~50% to the total consumption of DO in near-bottom water. At shorter than seasonal time scales on the inner shelf, along-shelf advection of hypoxic patches and cross-shelf advection of seasonal gradients are both shown to be important, changing DO concentrations by 1.5 mL/L or more over five days. PMID:20463844

Changes in upwelling and surface productivity in the Eastern Pacific during Terminations I and II

NASA Astrophysics Data System (ADS)

Erdem, Z.; De Bar, M.; Stolwijk, D.; Schneider, R. R.; S Sinninghe Damsté, J.; Schouten, S.

2017-12-01

The Eastern Pacific coastal system is characterized by intense upwelling and consequently by an enhanced surface primary productivity. Combination of this high organic matter flux with sluggish bottom water ventilation results in one of the most pronounced oxygen minimum zones reaching from offshore California in the North to offshore Chile in the South. As a result of this process, the region is particularly interesting in view of nutrient and carbon cycling as well as ecosystem dynamics. The dynamics of the upwelling and oxygen concentrations are closely related to climatic conditions. Therefore, paleo-reconstructions of different settings are crucial in order to improve our understanding of the response of these nutrient-rich, oxygen-deficient, environments in relation to the recent global ocean warming, acidification and deoxygenation. In this study, we present downcore results from three different sites in the Eastern Pacific: offshore California (IODP site 1012), Peru (M77/2-52-2) and Chile (IODP site 1234). We applied different biomarkers as proxies to decipher changes in phytoplankton community composition, including the upwelling index based on long chain diols, and other common productivity indicators such as bulk organic carbon, carbonate and biogenic opal. In addition, application of carbon and nitrogen isotope ratios of total organic carbon and benthic foraminifera complement our multiproxy approach. Herewith we aim to compare at least two glacial-interglacial transitions with different magnitudes of deglacial warming along the Eastern Pacific upwelling systems at different latitudes. The data presented will cover the last 160 ka BP offshore California and Chile, and 30 ka BP offshore Peru enabling comparison between glacial Terminations I and II.

Wind influence on a coastal buoyant outflow

NASA Astrophysics Data System (ADS)

Whitney, Michael M.; Garvine, Richard W.

2005-03-01

This paper investigates the interplay between river discharge and winds in forcing coastal buoyant outflows. During light winds a plume influenced by the Earth's rotation will flow down shelf (in the direction of Kelvin wave propagation) as a slender buoyancy-driven coastal current. Downwelling favorable winds augment this down-shelf flow, narrow the plume, and mix the water column. Upwelling favorable winds drive currents that counter the buoyancy-driven flow, spread plume waters offshore, and rapidly mix buoyant waters. Two criteria are developed to assess the wind influence on a buoyant outflow. The wind strength index (Ws) determines whether a plume's along-shelf flow is in a wind-driven or buoyancy-driven state. Ws is the ratio of the wind-driven and buoyancy-driven along-shelf velocities. Wind influence on across-shelf plume structure is rated with a timescale (ttilt) for the isopycnal tilting caused by wind-driven Ekman circulation. These criteria are used to characterize wind influence on the Delaware Coastal Current and can be applied to other coastal buoyant outflows. The Delaware buoyant outflow is simulated for springtime high-river discharge conditions. Simulation results and Ws values reveal that the coastal current is buoyancy-driven most of the time (∣Ws∣ < 1 on average). Wind events, however, overwhelm the buoyancy-driven flow (∣Ws∣ > 1) several times during the high-discharge period. Strong upwelling events reverse the buoyant outflow; they constitute an important mechanism for transporting fresh water up shelf. Across-shelf plume structure is more sensitive to wind influence than the along-shelf flow. Values of ttilt indicate that moderate or strong winds persisting throughout a day can modify plume width significantly. Plume widening during upwelling events is accompanied by mixing that can erase the buoyant outflow.

The role of sea surface circulation and hydrographic processes in anchovy spawning and larvae distribution in the Strait of Sicily (Central Mediterranean).

NASA Astrophysics Data System (ADS)

Falcini, Federico; Palatella, Luigi; Cuttitta, Angela; Bignami, Francesco; Patti, Bernardo; Santoleri, Rosalia; Fiorentino, Fabio

2014-05-01

The European Anchovy (Engraulis encrasicolus, Linnaeus, 1758) is one of the most important resources of the Mediterranean Sea. Despite its abundance and relevance, the anchovy population off the Mediterranean coasts exhibits a patchy distribution. Moreover, its biology and the influence of environment on its variability is poorly known. We here use data from ichthyoplankton-surveys carried out during the peak spawning season in order to analyze abundance and age of anchovy larvae in the Strait of Sicily, with respect to sea surface dynamic and hydrographic parameter patterns. The Strait of Sicily dynamics is characterized by upwelling regions, fronts, vortices, and filaments, with a consequent complexity in the spatial distribution of oceanographic parameters and anchovy larvae. To investigate the role of mesoscale features and oceanographic environment on the latter, anchovy larvae observations were paired to remote sensing data (such as sea surface temperature, chlorophyll, primary production, surface wind speed as well as light attenuation, absorption, and particle backscattering coefficients) and Lagrangian and Eulerian numerical simulations results for ocean currents and larval transport. The subsequent analysis shows and quantifies how the Atlantic Ionian Stream (AIS, a meandering current of Atlantic origin) path and variability, as well as the upwelling-induced south Sicilian coastal current, have consequences for anchovy spawning and larvae distribution. These currents transport anchovy larvae towards the Sicilian coast's south-eastern tip, where larvae are then retained in a frontal structure. However, significant cross-shore transport events due to relatively cold filament-like baroclinic instabilities generated by wind-induced coastal upwelling were also observed. Finally, the larval age distribution qualitatively agrees well with this transport pattern.

Sediment transport dynamics at the Ria de Vigo inferred from two mooring stations

NASA Astrophysics Data System (ADS)

Campistegui, Aimar; Bernabeu, Ana; Rey, Daniel

2010-05-01

The aim of this study is to characterise bottom currents and associated seafloor sediments at the Ría de Vigo, a 28 km long by 12 km wide funnel shaped coastal embayments at the NW coast of the Iberian Peninsula. The embayment is south-westerly oriented, against the general northerly trend of the main coast, and partially closed at its mouth by the Cies Islands. Forms a wide U-valley with central depths varying from 10 to 60 m. Hydrodynamics shows a semidiurnal mesotidal regime, negative estuarine circulation; and important south-western wave climate component, particularly in winter. Coarse sediments are mostly siliciclastic-bioclastic carbonates mixtures and are preferentially distributed at shallow depths parallel to the coast. Fine grained sediments mostly consist of mud and are preferentially distributed in the most internal parts and occupying the deep central parts of the embayment. The survey was carried mooring two stations at the inner and outer parts of the embayment, the later quite close to the southern mouth. In each station the current velocity and direction, salinity, temperature, turbidity, pressure and dissolved oxygen were measured near the bottom. The survey period covered two weeks, from June 28th till July 11th of 2005. Surficial sediment grain size was characterised in representative sediment samples from different points of the ría, including the stations sites, using box corers. The analyzed temperature and salinity data show an upwelling process, taking place since the third day on, registering low temperature values, about 13°C and high salinity values, about 36.5 ppt. During the non-upwelling period the bottom current direction in both stations was different, NE during the flood SW during the ebb, at the station 1 and eastwards during the flood and SW during the ebb at the station 2. But during the upwelling period was the same at both stations, NE-SW. At the same time the velocity during whole survey period was higher in the first station than in the second station. The grain size at the second outermost station was coarse sand and mostly muds in the innermost. The results indicate that there are one or more factors affecting the current direction at the bottom at the station 2 which make it change during the non-upwelling period but not during the upwelling period. This implies a different transport direction of the fine sediment for each period. The calculated shear stress at this station indicates no transport by tidal currents, and subsequently that the main transport mechanism is dominated by waves in the area. This work was supported by projects PGIDIT06TAM31201PR of the Xunta de Galicia and TOPOSEDPROX and PROMARES and MICINN of the Spanish Goverment and ANCORIM, BIOREM and OILDEBEACH of the EU

Regional turbulence patterns driven by meso- and submesoscale processes in the Caribbean Sea

NASA Astrophysics Data System (ADS)

C. Pérez, Juan G.; R. Calil, Paulo H.

2017-09-01

The surface ocean circulation in the Caribbean Sea is characterized by the interaction between anticyclonic eddies and the Caribbean Upwelling System (CUS). These interactions lead to instabilities that modulate the transfer of kinetic energy up- or down-cascade. The interaction of North Brazil Current rings with the islands leads to the formation of submesoscale vorticity filaments leeward of the Lesser Antilles, thus transferring kinetic energy from large to small scales. Within the Caribbean, the upper ocean dynamic ranges from large-scale currents to coastal upwelling filaments and allow the vertical exchange of physical properties and supply KE to larger scales. In this study, we use a regional model with different spatial resolutions (6, 3, and 1 km), focusing on the Guajira Peninsula and the Lesser Antilles in the Caribbean Sea, in order to evaluate the impact of submesoscale processes on the regional KE energy cascade. Ageostrophic velocities emerge as the Rossby number becomes O(1). As model resolution is increased submesoscale motions are more energetic, as seen by the flatter KE spectra when compared to the lower resolution run. KE injection at the large scales is greater in the Guajira region than in the others regions, being more effectively transferred to smaller scales, thus showing that submesoscale dynamics is key in modulating eddy kinetic energy and the energy cascade within the Caribbean Sea.

Physical and biogeochemical variability in Todos Santos Bay, northwestern Baja California, derived from a numerical NPZD model

NASA Astrophysics Data System (ADS)

Cruz-Rico, Jorge; Rivas, David

2018-07-01

A physical-biogeochemical Nitrate-Phytoplankton-Zooplankton-Detritus (NPZD) numerical model is used to study the variability of coastal phytoplankton biomass in northwestern Baja California and the Todos Santos Bay (TSB), a region of high socioeconomic importance located in the southern California Current System. The model reproduces adequately the most important oceanographic features of the study area, like the coastal chlorophyll-a (Chl-a) maxima and thermal gradients in the regions of enhanced coastal upwelling. The variability of Chl-a in the TSB is influenced by the activity of El Niño-Southern Oscillation (ENSO) and decadal modes of the Pacific, e.g., the Pacific Decadal Oscillation (PDO) and the North Pacific Gyre Oscillation (NPGO). From de multi-year model simulation (2004-2011), this large-scale influence is remarkable in two contrasting anomalous years. The year 2006 was anomalously warm and with low Chl-a levels, associated with warm phases of ENSO and PDO and a weakening of the NPGO. These climatic anomalies caused a strong stratification and weak upwelling around the TSB, which induced a poor nutrient input into the Bay and a deep and weak subsurface Chl-a maximum (SCM) during summer. The year 2011, on the other hand, was a cold year with enhanced upwelling during the spring, associated with cold phases of ENSO and PDO and an intensification of the NPGO. These conditions also caused a weak stratification and an intense nutrient transport into the TSB and hence a shallower and stronger SCM.

Synoptic forcing of wind relaxations at Pt. Conception, California

NASA Astrophysics Data System (ADS)

Fewings, Melanie R.; Washburn, Libe; Dorman, Clive E.; Gotschalk, Christopher; Lombardo, Kelly

2016-08-01

Over the California Current upwelling system in summer, the prevailing upwelling-favorable winds episodically weaken (relax) or reverse direction for a few days. Near Pt. Conception, California, the wind usually does not reverse, but wind relaxation allows poleward oceanic coastal flow with ecological consequences. To determine the offshore extent and synoptic forcing of these wind relaxations, we formed composite averages of wind stress from the QuikSCAT satellite and atmospheric pressure from the North American Regional Reanalysis (NARR) using 67 wind relaxations during summer 2000-2009. Wind relaxations at Pt. Conception are the third stage of an event sequence that repeatedly affects the west coast of North America in summer. First, 5-7 days before the wind weakens near Pt. Conception, the wind weakens or reverses off Oregon and northern California. Second, the upwelling-favorable wind intensifies along central California. Third, the wind relaxes at Pt. Conception, and the area of weakened winds extends poleward to northern California over 3-5 days. The NARR underestimates the wind stress within ˜200 km of coastal capes by a factor of 2. Wind relaxations at Pt. Conception are caused by offshore extension of the desert heat low. This synoptic forcing is related to event cycles that cause wind reversal as in Halliwell and Allen (1987) and Mass and Bond (1996), but includes weaker events. The wind relaxations extend ˜600 km offshore, similarly to the California-scale hydraulic expansion fan shaping the prevailing winds, and ˜1000 km alongshore, limited by an opposing pressure gradient force at Cape Mendocino.

Seabird diversity hotspot linked to ocean productivity in the Canary Current Large Marine Ecosystem

PubMed Central

Attrill, Martin J.; Becker, Peter H.; Egevang, Carsten; Furness, Robert W.; Grémillet, David; Kopp, Matthias; Lescroël, Amélie; Matthiopoulos, Jason; Peter, Hans-Ulrich; Phillips, Richard A.

2016-01-01

Upwelling regions are highly productive habitats targeted by wide-ranging marine predators and industrial fisheries. In this study, we track the migratory movements of eight seabird species from across the Atlantic; quantify overlap with the Canary Current Large Marine Ecosystem (CCLME) and determine the habitat characteristics that drive this association. Our results indicate the CCLME is a biodiversity hotspot for migratory seabirds; all tracked species and more than 70% of individuals used this upwelling region. Relative species richness peaked in areas where sea surface temperature averaged between 15 and 20°C, and correlated positively with chlorophyll a, revealing the optimum conditions driving bottom-up trophic effects for seabirds. Marine vertebrates are not confined by international boundaries, making conservation challenging. However, by linking diversity to ocean productivity, our research reveals the significance of the CCLME for seabird populations from across the Atlantic, making it a priority for conservation action. PMID:27531154

Seabird diversity hotspot linked to ocean productivity in the Canary Current Large Marine Ecosystem.

PubMed

Grecian, W James; Witt, Matthew J; Attrill, Martin J; Bearhop, Stuart; Becker, Peter H; Egevang, Carsten; Furness, Robert W; Godley, Brendan J; González-Solís, Jacob; Grémillet, David; Kopp, Matthias; Lescroël, Amélie; Matthiopoulos, Jason; Patrick, Samantha C; Peter, Hans-Ulrich; Phillips, Richard A; Stenhouse, Iain J; Votier, Stephen C

2016-08-01

Upwelling regions are highly productive habitats targeted by wide-ranging marine predators and industrial fisheries. In this study, we track the migratory movements of eight seabird species from across the Atlantic; quantify overlap with the Canary Current Large Marine Ecosystem (CCLME) and determine the habitat characteristics that drive this association. Our results indicate the CCLME is a biodiversity hotspot for migratory seabirds; all tracked species and more than 70% of individuals used this upwelling region. Relative species richness peaked in areas where sea surface temperature averaged between 15 and 20°C, and correlated positively with chlorophyll a, revealing the optimum conditions driving bottom-up trophic effects for seabirds. Marine vertebrates are not confined by international boundaries, making conservation challenging. However, by linking diversity to ocean productivity, our research reveals the significance of the CCLME for seabird populations from across the Atlantic, making it a priority for conservation action. © 2016 The Authors.

Seasonal and annual variability of coastal sulphur plumes in the northern Benguela upwelling system

PubMed Central

Dadou, Isabelle

2018-01-01

We investigated the seasonal and annual variability of surface sulphur plumes in the northern Benguela upwelling system off Namibia because of their significant impacts on the marine ecosystem, fishing industry, aquaculture farming and tourism due to their toxic properties. We identified the sulphur plumes in ocean colour satellite data of the medium resolution imaging spectrometer (MERIS) for the 2002–2012 time period using the differences in the spectral properties of Namibian Benguela optical water types. The sulphur events have a strong seasonal cycle with pronounced main and off-seasons forced by local and remote-driven processes. The main peak season is in late austral summer and early austral autumn at the beginning of the annual upwelling cycle caused by increasing equatorwards alongshore winds. The sulphur plume activity is high between February and April during the seasonal oxygen minimum associated with the seasonal reduction of cross-shore ventilation of the bottom waters, the seasonal southernmost position of the Angola Benguela Frontal Zone, the seasonal maximum of water mass fractions of South Atlantic and Angola Gyre Central Waters as well as the seasonal arrival of the downwelling coastal trapped waves. The off-season is in austral spring and early austral summer during increased upwelling intensity and enhanced oxygen supply. The annual variability of sulphur events is characterized by very high activities in years 2004, 2005 and 2010 interrupted by periods of lower activity in years 2002 to 2003, 2006 to 2009 and 2011 to 2012. This result can be explained by the relative contributions or adding effects of local and remote-driven forces (from the equatorial area). The probability for the occurrence of sulphur plumes is enhanced in years with a lower annual mean of upwelling intensity, decreased oxygen supply associated with decreased lateral ventilation of bottom waters, more southern position of the Angola Benguela Frontal Zone, increased mass fraction of South Atlantic Central Water and stronger downwelling coastal trapped waves. Understanding of the variability and forcing processes of the toxic sulphur events will help in the future to monitor and forecast them as well as to manage their social and economic consequences in the northern Benguela upwelling system off Namibia. PMID:29420587

a Numerical Study of Basic Coastal Upwelling Processes.

NASA Astrophysics Data System (ADS)

Li, Zhihong

Available from UMI in association with The British Library. Two-dimensional (2-D) and three-dimensional (3 -D) numerical models with a second order turbulence closure are developed for the study of coastal upwelling processes. A logarithmic coordinate system is introduced to obtain increased resolution in the regions near the surface and bottom where high velocity shear occurs and in the upwelling zone where its width is confined to the coast. In the experiments performed in the 2-D model an ocean initially at rest is driven by a spatially uniform alongshore wind-stress. There is a development of an offshore flow in the surface layer and an onshore flow below the surface layer. In the wind-stress direction there is a development of a coastal surface jet. The neglect of the alongshore pressure gradient leads to the intensification of the jet, and the concentration of the onshore flow in an over-developed Ekman layer yielding an unrealistic deepening of a bottom mixed layer. When bathymetric variations are introduced, some modifications in the dynamics of upwelling are observed. On the shelf region there is another upwelling zone and isotherms are interested with the bottom topography. When an alongshore pressure gradient is added externally into the model, the strength of the coastal jet decreases and a coastal undercurrent exists at greater depth. In addition the return onshore flow is largely independent of depth and the deepening of the bottom mixed layer disappears. In the experiments performed in the 3-D model a wind-stress with limited domain is used. Coastally trapped waves are generated and propagate along the coastline leading to a development of an alongshore pressure gradient, which has a significant effect on upwelling. The evolution of the alongshore flow, vertical velocity and the temperature is determined by both remote and local wind due to the propagation of waves. As the integration proceeds, the flow pattern becomes remarkably 3-dimensional. Finally the influence of bathymetric variations on upwelling processes is examined.

Bio-Optical Measurements in Upwelling Ecosystems in Support of SIMBIOS. Chapter 4

NASA Technical Reports Server (NTRS)

Chavez, Francisco P.; Strutton, Peter G.; Kuwahara, Victor S.; Mahoney, Kevin L.; Drake, Eric

2003-01-01

The upwelling region of the equatorial Pacific Ocean, which spans one quarter of the earth s circumference, strongly impacts global biogeochemistry. This upwelling system has significant implications for global CO2 fluxes (Tans et al., 1990; Takahashi et al., 1997; Feely et al., 1999), as well as primary and secondary production (Chavez and Barber, 1987; Chavez and Toggweiler, 1995; Chavez et al., 1996; Dugdale and Wilkerson, 1998; Chavez et al., 1999; Strutton and Chavez, 2000). In addition, the region represents a vast oceanic (case 1) region over which validation data for SeaWiFS are needed. This project consists of an optical mooring program and cruise-based measurements focused on measuring biological and chemical variability in the equatorial Pacific and obtaining validation data for SeaWiFS.

A review of climate change impacts on birds

Treesearch

Robert W. Butler; William Taylor

2005-01-01

Regions of the world with high coastal zone biological productivity often support large numbers of birds. Important sources of this productivity are oceanographic upwelling created by winds and ocean currents, and runoff from the land. It is suggested that climate change effects on winds and ocean currents will potentially affect the timing and magnitude of coastal...

Humpback whale diets respond to variance in ocean climate and ecosystem conditions in the California Current.

PubMed

Fleming, Alyson H; Clark, Casey T; Calambokidis, John; Barlow, Jay

2016-03-01

Large, migratory predators are often cited as sentinel species for ecosystem processes and climate-related changes, but their utility as indicators is dependent upon an understanding of their response to environmental variability. Documentation of the links between climate variability, ecosystem change and predator dynamics is absent for most top predators. Identifying species that may be useful indicators and elucidating these mechanistic links provides insight into current ecological dynamics and may inform predictions of future ecosystem responses to climatic change. We examine humpback whale response to environmental variability through stable isotope analysis of diet over a dynamic 20-year period (1993-2012) in the California Current System (CCS). Humpback whale diets captured two major shifts in oceanographic and ecological conditions in the CCS. Isotopic signatures reflect a diet dominated by krill during periods characterized by positive phases of the North Pacific Gyre Oscillation (NPGO), cool sea surface temperature (SST), strong upwelling and high krill biomass. In contrast, humpback whale diets are dominated by schooling fish when the NPGO is negative, SST is warmer, seasonal upwelling is delayed and anchovy and sardine populations display increased biomass and range expansion. These findings demonstrate that humpback whales trophically respond to ecosystem shifts, and as a result, their foraging behavior is a synoptic indicator of oceanographic and ecological conditions across the CCS. Multi-decadal examination of these sentinel species thus provides insight into biological consequences of interannual climate fluctuations, fundamental to advancing ecosystem predictions related to global climate change. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Wind stress and heat fluxes over a Brazilian Coastal Upwelling

NASA Astrophysics Data System (ADS)

Dourado, Marcelo; Candella, Rogério

2017-04-01

Coastal upwelling zones have been intensively studied in the last decades especially due to their importance to the biological cycle. The coastal upwelling system of the Cabo Frio region (east coast of the Rio de Janeiro state, Brazil) keeps the surface water cold during most part of the year, what induces a stable atmospheric boundary layer associated to northeast winds. The main goal of this study is to investigate the wind stress and heat fluxes exchanges between the ocean and the atmosphere in that area. For this purpose, a set of hourly data meteorological and oceanographic data collected by a Wavescan metocean buoy anchored at 23o59S; 42oW, were used, as well as solar radiation and relative humidity from a terrestrial meteorological station from the Instituto Nacional de Meteorologia (InMet). COARE 3.0 algorithm was used to calculate the latent and sensible heat fluxes. In this discussion, positive values represent fluxes towards the ocean. The average net heat flux over our study period is 88 W m-2. The reduction of the net heat flux is due to the increase of the ocean latent heat loss, although a reduction in incoming shortwave radiation and an increase in ocean long wave cooling also contributes. The latent heat is 20 times larger than the sensible heat flux, but the mean value of the latent heat flux, 62 W m-2, is half the typical value found in open ocean. The temporal variability of both sensible and latent heat fluxes reflects their dependence on wind speed and air-sea temperature differences. When upwelling events, here periods when diurnal SST is lower than 18oC, are compared with undisturbed (without upwelling) events, it can be noted the sensible heat fluxes are positives and 10 times greater in magnitude. This is related to an increment, during these upwelling events, of the air-sea temperature difference and an increasing of the wind speed. The cold waters of the upwelling increase the air-sea temperature gradient and, also, the horizontal land-sea gradient. This could intensifies the sea breeze. At the same time, the latent heat flux to the atmosphere is reduced. As expected, cold waters from the upwelling imply in the reduction of the evaporation, and so the latent heat fluxes also reduce significantly. As upwelling events in this region are associated to the presence of the South Atlantic high pressure, NE winds, during these periods of cold water the net heat flux toward the ocean surface is intensified.

Estuary-ocean connectivity: Fast physics, slow biology

USGS Publications Warehouse

Raimonet, Mélanie; Cloern, James E.

2017-01-01

Estuaries are connected to both land and ocean so their physical, chemical, and biological dynamics are influenced by climate patterns over watersheds and ocean basins. We explored climate-driven oceanic variability as a source of estuarine variability by comparing monthly time series of temperature and chlorophyll-a inside San Francisco Bay with those in adjacent shelf waters of the California Current System (CCS) that are strongly responsive to wind-driven upwelling. Monthly temperature fluctuations inside and outside the Bay were synchronous, but their correlations weakened with distance from the ocean. These results illustrate how variability of coastal water temperature (and associated properties such as nitrate and oxygen) propagates into estuaries through fast water exchanges that dissipate along the estuary. Unexpectedly, there was no correlation between monthly chlorophyll-a variability inside and outside the Bay. However, at the annual scale Bay chlorophyll-a was significantly correlated with the Spring Transition Index (STI) that sets biological production supporting fish recruitment in the CCS. Wind forcing of the CCS shifted in the late 1990s when the STI advanced 40 days. This shift was followed, with lags of 1–3 years, by 3- to 19-fold increased abundances of five ocean-produced demersal fish and crustaceans and 2.5-fold increase of summer chlorophyll-a in the Bay. These changes reflect a slow biological process of estuary–ocean connectivity operating through the immigration of fish and crustaceans that prey on bivalves, reduce their grazing pressure, and allow phytoplankton biomass to build. We identified clear signals of climate-mediated oceanic variability in this estuary and discovered that the response patterns vary with the process of connectivity and the timescale of ocean variability. This result has important implications for managing nutrient inputs to estuaries connected to upwelling systems, and for assessing their responses to changing patterns of upwelling timing and intensity as the planet continues to warm.

Can upwelling signals be detected in intertidal fishes of different trophic levels?

PubMed

Pulgar, J; Poblete, E; Alvarez, M; Morales, J P; Aranda, B; Aldana, M; Pulgar, V M

2013-11-01

For intertidal fishes belonging to three species, the herbivore Scartichthys viridis (Blenniidae), the omnivore Girella laevifrons (Kyphosidae) and the carnivore Graus nigra (Kyphosidae), mass and body size relationships were higher in individuals from an upwelling zone compared with those from a non-upwelling zone. RNA:DNA were higher in the herbivores and omnivores from the upwelling zone. Higher biomass and RNA:DNA in the upwelling intertidal fishes may be a consequence of an increased exposure to higher nutrient availability, suggesting that increased physiological conditioning in vertebrates from upwelling areas can be detected and measured using intertidal fishes of different trophic levels. © 2013 The Fisheries Society of the British Isles.

Seasonality in planktic foraminifera of the central California coastal upwelling region

NASA Astrophysics Data System (ADS)

Davis, Catherine V.; Hill, Tessa M.; Russell, Ann D.; Gaylord, Brian; Jahncke, Jaime

2016-09-01

The close association between planktic foraminiferal assemblages and local hydrography make foraminifera invaluable proxies for environmental conditions. Modern foraminiferal seasonality is important for interpreting fossil distributions and shell geochemistry as paleoclimate proxies. Understanding this seasonality in an active upwelling area is also critical for anticipating which species may be vulnerable to future changes in upwelling intensity and ocean acidification. Two years (2012-2014) of plankton tows, along with conductivity-temperature-depth profiles and carbonate chemistry measurements taken along the north-central California shelf, offer new insights into the seasonal dynamics of planktic foraminifera in a seasonal coastal upwelling regime. This study finds an upwelling affinity for Neogloboquadrina pachyderma as well as a seasonal and upwelling associated alternation between dominance of N. pachyderma and Neogloboquadrina incompta, consistent with previous observations. Globigerina bulloides, however, shows a strong affinity for non-upwelled waters, in contrast to findings in Southern California where the species is often associated with upwelling. We also find an apparent lunar periodicity in the abundances of all species and document the presence of foraminifera even at very low saturation states of calcite.

Development of upwelling on pathway and freshwater transport of Pearl River plume in northeastern South China Sea

NASA Astrophysics Data System (ADS)

Chen, Zhaoyun; Jiang, Yuwu; Liu, James T.; Gong, Wenping

2017-08-01

In situ observations, satellite images, and numerical modeling results have shown that the Pearl River plume axis extends alongshore and passes through two separate upwelling regions—one off the Guangdong and Fujian coasts (the Yuedong upwelling) and the other in the Taiwan Bank during the initial and medium stages of the Yuedong upwelling, while it is directed offshore when the Yuedong upwelling is strong. Model experiments are conducted to examine the effects of wind strength and baroclinicity on the upwelling and the corresponding pathway and freshwater transport of the Pearl River plume. The baroclinic effect is important to intensifying the horizontal velocity at the upwelling front and freshwater transport in the northeastern South China Sea. The freshwater transport flux is further decomposed into advection, vertical shear, and tidal pumping components, and advection is the dominant contributor. As the Yuedong upwelling develops, the zone with a relatively high-pressure gradient moves offshore due to offshore Ekman transport and the shift in the upwelling front, which is responsible for the offshore transport of the river plume. When the river plume is transported to the outer-shelf, sometimes it can be further entrained into eddies, allowing its export to the open sea.

Spatio-temporal variability of upwelling along the southwest coast of India based on satellite observations

NASA Astrophysics Data System (ADS)

Jayaram, Chiranjivi; Kumar, P. K. Dinesh

2018-03-01

Upwelling phenomenon along the eastern boundaries of global ocean has received greater attention in the recent times due to its environmental and economic significance in the global warming and the scenario of changing climate as opined by IPCC AR5. In this context, the availabile satellite data on sea surface winds, sea surface temperature (SST), sea level anomaly (SLA) and chlorophyll-a concentration (Chl-a), for the period 1981-2016 were analyzed to identify the coastal upwelling pattern in the Southeastern Arabian Sea (SEAS). Synergistic approach, using winds, SST, SLA and Chl-a revealed that strong upwelling was prevailing between 8°N and 12°N. During the study period, geographical differences existed in the peak values of upwelling favorable conditions considered for study. Analysis of the alongshore winds which are conducive for upwelling were observed to be curtailed towards the northern part of the study region between 2005 and 2010. Also, the strength of upwelling reduced during the strong ENSO years of 1997 and 2015. Linear regression based trend analysis of upwelling indices like Ekman transport, SST and chlorophyll along the coast, during the upwelling period, revealed slight increase in the strength towards the southern region while it decreased to the north during the study period.

Controls on Mixing-Dependent Denitrification in Hyporheic Zones

NASA Astrophysics Data System (ADS)

Hester, E. T.; Young, K. I.; Widdowson, M. A.

2013-12-01

Interaction of surface water and groundwater in hyporheic sediments of river systems is known to create unique biogeochemical conditions that can attenuate contaminants flowing downstream. Oxygen, carbon, and the contaminants themselves (e.g., excess nitrate) often advect together through the hyporheic zone from sources in surface water. However, the ability of the hyporheic zone to attenuate contaminants in upwelling groundwater plumes as they exit to rivers is less known. Such reactions may be more dependent on mixing of carbon and oxygen sources from surface water with contaminants from deeper groundwater. We simulated hyporheic flow cells and upwelling groundwater together with mixing-dependent denitrification of an upwelling nitrate plume in shallow riverbed sediments using MODFLOW and SEAM3D. For our first set of model scenarios, we set biogeochemical boundary conditions to be consistent with situations where only mixing-dependent denitrification occurred within the model domain. This occurred where dissolved organic carbon (DOC) advecting from surface water through hyporheic flow cells meets nitrate upwelling from deeper groundwater. This would be common where groundwater is affected by septic systems which contribute nitrate that upwells into streams that do not have significant nitrate sources from upstream. We conducted a sensitivity analysis that showed that mixing-dependent denitrification increased with parameters that increase mixing itself, such as the degree of heterogeneity of sediment hydraulic conductivity (K). Mixing-dependent denitrification also increased with certain biogeochemical boundary concentrations such as increasing DOC or decreasing dissolved oxygen (DO) advecting from surface water. For our second set of model scenarios, we set biogeochemical boundary conditions to be consistent with common situations where non-mixing-dependent denitrification also occurred within the model domain. For example, when nitrate concentrations are substantial in water advecting from surface water, non-mixing-dependent denitrification can occur within the hyporheic flow cells. This would be common where surface water and groundwater have high nitrate concentrations in agricultural areas. We conducted a sensitivity analysis for this set of model scenarios as well, to evaluate controls on the relative balance of mixing-dependent and non-mixing-dependent denitrification. We found that non-mixing-dependent denitrification often has higher potential to consume nitrate than mixing-dependent denitrification. This is because non-mixing-dependent denitrification is not confined to the relatively small mixing zone between upwelling groundwater and hyporheic flow cells, and hence often has longer residence times available for consumption of existing oxygen followed by consumption of nitrate. Nevertheless, the potential for hyporheic zones to attenuate upwelling nitrate plumes appears to be substantial, yet is variable depending on geomorphic, hydraulic, and biogeochemical conditions.

Variability of temperature and chlorophyll of the Iberian Peninsula near costal ecosystem during an upwelling event for the present climate and a future climate scenario

NASA Astrophysics Data System (ADS)

Lopes, José Fortes; Ferreira, Juan A.; Cardoso, Ana Cristina; Rocha, Alfredo C.

2014-01-01

Understanding the importance and the implication of the climate changes on coastal areas may be one of the major issues for this and next centuries. Climate changes may, indeed, impact the nearshore marine ecosystem, as coastal areas are very sensitive to the strength and the variability of the meteorological forcings. The main purpose of this work is to study temperature and phytoplankton distributions along the Portuguese near coastal zone during upwelling events in the present climate conditions and in a future climate scenario. The SRES-A2 IPCC scenario has been considered. We have used a three-dimensional model for coastal and shelf seas, including the following sub-models: hydrodynamical/physical, biological, sediment and contaminant. The forcings are provided by the interactions at the air-sea, considering the wind intensity and direction with the help of the WRF model (Weather Research and Forecast Model) and the coupled atmosphere-ocean model ECHAM5/MPI-OM. Results show that, for the future climate scenario, there is a reinforcement of the southward wind. The responses of the coastal ecosystem corresponds to the reinforcement of both, the southward (up to 10 cm/s) and the westward (up to 6 cm/s) induced upwelling currents. This, in turn generates an enlargement of the near coast upwelled cold layer, extending up to 60 km, as well as the rise of the warm layer temperature (up to 2.0 °C) and the spreading of the phytoplankton offshore. Significant changes in both the Chl-a vertical and the horizontal distribution patterns have been observed, as the nutrient supply to the upper layers depends on the strength of the upwelling, the bottom topography and orography of the coastal. These results confirm that changes in the strength and eventually the frequency of the upwelling favourable wind impact the phytoplankton distribution, which can have significant effect in the distribution and population of the upper level of the trophic chain of the coastal ecosystem.

Eastern Boundary Upwelling Ecosystems: Review and Observing Needs

NASA Astrophysics Data System (ADS)

Chavez, F.; Garçon, V. C.; Dewitte, B.; Montes, I.

2015-12-01

Eastern Boundary Upwelling Systems (EBUS) cover less than 3% of the world ocean surface but play a significant role in the climate system, and contribute disproportionately to ocean biological productivity with up to 40% of the reported global fish catch. Coupled with the vast coastal human populations, these regions play key socio-economic roles. Human pressure on these productive ecosystems and their services is increasing, requiring new and evolving scientific approaches to collect information and use it in management. Here we review and compare the physical, chemical and biological characteristics of the four major EBUS: Benguela, California, Northwest Africa and Peru/Chile. Long-term trends and climate variability are emphasized. Technologies and systems for observing and understanding the changing marine ecosystems of EBUS are discussed.

Long-time observation of annual variation of Taiwan Strait upwelling in summer season

NASA Astrophysics Data System (ADS)

Tang, D. L.; Kawamura, H.; Guan, L.

The Taiwan Strait is between Taiwan Island and Mainland China, where several upwelling zones are well known for good fishing grounds. Earlier studies in the strait have been conducted on detecting upwelling by ship measurements with short-term cruises, but long-term variations of upwelling in this region are not understood. The present paper examines satellite images for a long-time observation of two major upwelling zones in the Taiwan Strait: Taiwan Bank Upwelling (TBU) and Dongshan Upwelling (DSU). Sea surface temperature (SST) and chlorophyll a (Chl-a) images have been analyzed for summer months (June, July, and August) from 1980 to 2002. Results reveal annual variation of two upwelling zones. These two upwelling zones occur every year characterized with distinct low water temperature and high Chl-a concentrations. During the period from 1989 to 1998, SST is found to be 1.15 °C lower in TBU, and 1.42 °C lower in the DSU than the Taiwan Strait. The size of DSU has been found to be larger during summer of 1989, 1990, 1993 and 1995; TBU has been found to be weak during summer of 1994 and 1997. Ocean color images obtained from CZCS, OCI, and SeaWiFS also show high Chl-a concentrations (0.8-2.5 mg m-3) in two upwelling zones, which coincide with low SST in terms of location, shape, and time. These high Chl-a concentrations in TBU and DSU may be related to upwelling waters that bring nutrients from bottom to surface. The present results also show the potential of using satellite data for monitoring of ocean environment for long time period.

Contrasting Responses of the Humboldt Current Ecosystem between the Holocene and MIS5e Interglacials Revealed from Multiple Sediment Records

NASA Astrophysics Data System (ADS)

Salvatteci, R.; Schneider, R. R.; Blanz, T.; Martinez, P.; Crosta, X.

2016-12-01

The Humboldt Current Ecosystem (HCE) off Peru yields about 10% of the global fish catch, producing more fish per unit area than any other region in the world. The high productivity is maintained by the upwelling of cold, nutrient-rich water from the oxygen minimum zone (OMZ), driven by strong trade winds. However, the potential impacts of climate change on upwelling dynamics and oceanographic conditions in the near future are uncertain, threatening local and global economies. Here, we unravel the response of the HCE to contrasting climatic conditions during the last two interglacials (i.e. Holocene and MIS5e) providing an independent insight about the relation between climatic factors and upwelling and productivity dynamics. For this purpose, we used multiple cores to reconstruct past changes in OMZ and upwelling intensity, productivity and fish biomass variability. Chronologies for the Holocene were obtained by multiple 14C ages and laminae correlations among cores, while for the MIS5e they were mainly done by correlation of prominent features in several proxies with other published records. We used a multiproxy approach including alkenones to reconstruct sea surface temperatures, δ15N as a proxy for water column denitrification, redox sensitive metals as proxies for sediment redox conditions, and diatom and fish debris assemblages to reconstruct ecological changes. The results show a very different response of the HCE to climate conditions during the last 2 interglacials, likely driven by changes in Tropical Pacific dynamics. During the Holocene we find that 1) the Late Holocene exhibits higher multi-centennial scale variability compared to the Early Holocene, 2) increased upwelling and a weak OMZ during the mid-Holocene, and 3) long term increase in productivity (diatoms and fishes) from the Early to the Late Holocene. During the MIS5e we find an 1) intense OMZ, 2) strong water column stratification, 3) high siliceous biomass, and 4) low fish biomass compared to the Holocene and a regime shift towards more hemipelagic fishes. Our paleoreconstructions during the globally warm MIS5e are consistent with models indicating that the expected increase in stratification and atmospheric CO2 concentrations may significantly reduce fish capacity in the HCE with heavy ecological and economic consequences.

Surface distribution of brachyuran megalopae and ichthyoplankton in the Columbia River plume during transition from downwelling to upwelling conditions

NASA Astrophysics Data System (ADS)

Roegner, G. Curtis; Daly, Elizabeth A.; Brodeur, Richard D.

2013-06-01

In the California Current coastal boundary zone, the spring transition between downwelling and upwelling conditions, along with the fluctuating structure of the Columbia River plume, creates highly dynamic interactions. In this study, we investigated whether the surface distribution of brachyuran larvae and ichthyoplankton would track the dynamics of the Columbia River plume. By happenstance, the cruise period coincided with the spring transition from downwelling to sustained upwelling conditions in 2010, a year when the transition was delayed and Columbia River flow was substantially higher than average. We used time series of wind and freshwater input to evaluate the influence of physical forcing on oceanographic patterns, and sampled hydrography and surface plankton concentrations within a 182 km2 grid off Willapa Bay, WA. Additionally, two longer transects, one cross-shelf and the other along-shore, were made to discern the extent of plume influence on larval crab and fish abundance. We found that plume waters that were trapped in a northward-flowing coastal-boundary current during downwelling conditions were advected offshore after several days of upwelling-favorable winds. Neustonic collections of brachyuran larvae and ichthyoplankton varied in response to this large seaward advective event. Megalopae of cancrid crabs exhibited patterns of both offshore transport (Cancer oregonensis/productus) and nearshore retention (C. magister). Additionally, abundant numbers of large juvenile widow (Sebastes entomelas) and yellowtail (S. flavidus) rockfish of a size appropriate for settlement were sampled during a period when ocean conditions favored high recruitment success. These results demonstrated that the response of planktonic crab larvae and ichthyoplankton to large-scale advection varied by species, with larger and more vagile fish exhibiting less evidence of passive transport than smaller crab larvae. Importantly, portions of the planktonic fish and crab community were able to maintain nearshore distributions in favorable settlement habitat, despite physical advection offshore.

BOREAS AFM-1 NOAA/ATDD Long-EZ Aircraft Flux data Over the SSA

NASA Technical Reports Server (NTRS)

Crawford, Timothy L.; Baldocchi, Dennis; Hall, Forrest G. (Editor); Knapp, David E. (Editor); Gunter, Laureen; Dumas, Ed; Smith, David E. (Technical Monitor)

2000-01-01

This data set contains measurements from the Airborne Flux and Meteorology (AFM)-1 National Oceanographic and Atmospheric Administration/Atmospheric Turbulence and Diffusion Division (NOAA/ATDD) Long-EZ Aircraft collected during the 1994 Intensive Field Campaigns (IFCs) at the southern study area (SSA). These measurements were made from various instruments mounted on the aircraft. The data that were collected include aircraft altitude, wind direction, wind speed, air temperature, potential temperature, water mixing ratio, U and V components of wind velocity, static pressure, surface radiative temperature, downwelling and upwelling total radiation, downwelling and upwelling longwave radiation, net radiation, downwelling and upwelling photosynthectically active radiation (PAR), greenness index, CO2 concentration, O3 concentration, and CH4 concentration. There are also various columns that indicate the standard deviation, skewness, kurtosis, and trend of some of these data. The data are stored in tabular ASCII files. The NOAA/ATDD Long-EZ aircraft flux data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

High-resolution paleoclimatology of the coastal margin of northernmost California during the past 7,300 years

NASA Astrophysics Data System (ADS)

Barron, J. A.; Heusser, L. E.; Addison, J. A.; Burky, D.; Kusler, J. E.; Finney, B.

2013-12-01

Piston core TN062 0550, located 13 km offshore of Eureka, California (40.866 deg. N, 124.572 deg. W, 550 m water depth), contains a continuous high-resolution climate record of the past 7,300 yr. Deposition occurred at nearly constant sedimentation rates averaging 94 cm/kyr based on 14C AMS dating of planktonic foraminifers. Pollen and marine ecosystem proxies (diatoms, silicoflagellates, wt. percent biogenic silica) studied at 50-70 yr sample resolution show a stepwise development of the climate/ oceanographic system off northernmost California. The relative contributions of Sequoia sempervirens (coastal redwood) pollen, a proxy for coastal fog associated with offshore upwelling, and biogenic silica concentrations (a proxy for siliceous export productivity) increase (two fold and three fold, respectively) in successive steps at ~5,000 yr BP and from ~2,400 to 2,000 yr BP. These increases are interpreted to reflect a progressive intensification of spring upwelling based on modern observations of the California Current system. At 5,000 yr BP diatom assemblages change from an assorted mixture of warm, temperate, and cool-water taxa to a low diversity temperate-oceanic assemblage dominated by Thalassionema spp. At ~2,400 yr BP the diatom assemblage transitions to a mixture of nearshore upwelling taxa and taxa associated with the central North Pacific Gyre. Silicoflagellate assemblages undergo a similar increase in the representation of modern seasonal proxies at ~3,000 yr BP that may reflect intensified ENSO variability. A two-fold increase in the relative contributions of Quercus (oak) and riparian Alnus (alder) pollen between ~3,800 and 2,000 yr BP likely signals a period of enhanced fluvial runoff associated with increased winter precipitation. Given the present day association of the Eel River system with the northwestern half of the western US winter precipitation dipole, these pollen data suggest that the ~3,800 and 2,000 yr interval was dominated by protracted negative Pacific Decadal Oscillation-like (PDO) conditions. The widespread occurrence of drought in the southwestern US between ~3,800 and 2,200 yr BP supports this interpretation.

Gulf of Mexico Loop Current Interactions with the West Florida Shelf and its Influence on Harmful Algae Blooms

NASA Astrophysics Data System (ADS)

Liu, Y.; Weisberg, R. H.

2016-02-01

Interactions of the Loop Current (LC) system with the West Florida Shelf (WFS) are examined using 20+ years (1993 - 2015) of Ssalto/Duacs multi-mission altimetry data in the eastern Gulf of Mexico. Characteristic patterns of LC system sea surface height and surface geostrophic currents are extracted by an unsupervised neural network, Self-Organizing Map, along with their frequencies of occurrence. These current patterns suggest linkages with harmful algae bloom occurrences as recorded by in situ K. brevis cell counts. It is argued that LC system interactions with the shelf slope play an important role in WFS ecology through the upwelling of new inorganic nutrients across the shelf break. This is particularly important when the LC impinges on the southwest corner of the WFS slope, thereby impacting shallow water isobaths and setting the entire shelf circulation into motion. If such conditions persist, then deeper ocean waters with elevated nutrient content may broach the shelf and be transported landward. Resetting the nutrient state of the shelf by the coastal ocean circulation in response to deep-ocean forcing demonstrates the importance of physical oceanography in shelf ecology.

High-Latitude Neutral Density Structures Investigated by Utilizing Multi-Instrument Satellite Data and NRLMSISE-00 Simulations

NASA Astrophysics Data System (ADS)

Horvath, Ildiko; Lovell, Brian C.

2018-02-01

This study investigates various types of neutral density features developed in the cusp region during magnetically active and quiet times. Multi-instrument Challenging Minisatellite Payload data provide neutral density, electron temperature, neutral wind speed, and small-scale field-aligned current (SS-FAC) values. Gravity Recovery and Climate Experiment neutral density data are also employed. During active times, cusp densities or density spikes appeared with their underlying flow channels (FCs) and enhanced SS-FACs implying upwelling, fueled by Joule heating, within/above FCs. Both the moderate nightside cusp enhancements under disturbed conditions and the minor dayside cusp enhancements under quiet conditions developed without any underlying FC and enhanced SS-FACs implying the role of particle precipitation in their development. Observations demonstrate the relations of FCs, density spikes, and upwelling-related divergent flows and their connections to the underlying (1) dayside magnetopause reconnection depositing magnetospheric energy into the high-latitude region and (2) Joule heating-driven disturbance dynamo effects. Results provide observational evidence that the moderate nightside cusp enhancements and the minor dayside cusp enhancements detected developed due to direct heating by weak particle precipitation. Chemical compositions related to the dayside density spike and low cusp densities are modeled by Naval Research Laboratory Mass Spectrometer Incoherent Scatter Radar Extended 2000. Modeled composition outputs for the dayside density spike's plasma environment depict some characteristic upwelling signatures. Oppositely, in the case of low dayside cusp densities, composition outputs show opposite characteristics due to the absence of upwelling.

El Niño and similar perturbation effects on the benthos of the Humboldt, California, and Benguela Current upwelling ecosystems

NASA Astrophysics Data System (ADS)

Arntz, W. E.; Gallardo, V. A.; Gutiérrez, D.; Isla, E.; Levin, L. A.; Mendo, J.; Neira, C.; Rowe, G. T.; Tarazona, J.; Wolff, M.

2006-03-01

To a certain degree, Eastern Boundary Current (EBC) ecosystems are similar: Cold bottom water from moderate depths, rich in nutrients, is transported to the euphotic zone by a combination of trade winds, Coriolis force and Ekman transport. The resultant high primary production fuels a rich secondary production in the upper pelagic and nearshore zones, but where O2 exchange is restricted, it creates oxygen minimum zones (OMZs) at shelf and upper slope (Humboldt and Benguela Current) or slope depths (California Current). These hypoxic zones host a specifically adapted, small macro- and meiofauna together with giant sulphur bacteria that use nitrate to oxydise H2S. In all EBC, small polychaetes, large nematodes and other opportunistic benthic species have adapted to the hypoxic conditions and co-exist with sulphur bacteria, which seem to be particularly dominant off Peru and Chile. However, a massive reduction of macrobenthos occurs in the core of the OMZ. In the Humboldt Current area the OMZ ranges between <100 and about 600 m, with decreasing thickness in a poleward direction. The OMZ merges into better oxygenated zones towards the deep sea, where large cold-water mega- and macrofauna occupy a dominant role as in the nearshore strip. The Benguela Current OMZ has a similar upper limit but remains shallower. It also hosts giant sulphur bacteria but little is known about the benthic fauna. However, sulphur eruptions and intense hypoxia might preclude the coexistence of significant mega- und macrobenthos. Conversely, off North America the upper limit of the OMZ is considerably deeper (e.g., 500-600 m off California and Oregon), and the lower boundary may exceed 1000m. The properties described are valid for very cold and cold (La Niña and "normal") ENSO conditions with effective upwelling of nutrient-rich bottom water. During warm (El Niño) episodes, warm water masses of low oxygen concentration from oceanic and equatorial regions enter the upwelling zones, bringing a variety of (sub)tropical immigrants. The autochthonous benthic fauna emigrates to deeper water or poleward, or suffers mortality. However, some local macrofaunal species experience important population proliferations, presumably due to improved oxygenation (in the southern hemisphere), higher temperature tolerance, reduced competition or the capability to use different food. Both these negative and positive effects of El Niño influence local artisanal fisheries and the livelihood of coastal populations. In the Humboldt Current system the hypoxic seafloor at outer shelf depths receives important flushing from the equatorial zone, causing havoc on the sulphur bacteria mats and immediate recolonisation of the sediments by mega- and macrofauna. Conversely, off California, the intruding equatorial water masses appear to have lower oxygen than ambient waters, and may cause oxygen deficiency at upper slope depths. Effects of this change have not been studied in detail, although shrimp and other taxa appear to alter their distribution on the continental margin. Other properties and reactions of the two Pacific EBC benthic ecosystems to El Niño seem to differ, too, as does the overall impact of major episodes (e.g., 1982/1983(1984) vs. 1997/1998). The relation of the "Benguela Niño" to ENSO seems unclear although many Pacific-Atlantic ocean and atmosphere teleconnections have been described. Warm, low-oxygen equatorial water seems to be transported into the upwelling area by similar mechanisms as in the Pacific, but most major impacts on the eukaryotic biota obviously come from other, independent perturbations such as an extreme eutrophication of the sediments ensuing in sulphidic eruptions and toxic algal blooms. Similarities and differences of the Humboldt and California Current benthic ecosystems are discussed with particular reference to ENSO impacts since 1972/73. Where there are data available, the authors include the Benguela Current ecosystem as another important, non-Pacific EBC, which also suffers from the effects of hypoxia.

On the subduction of oxygenated surface water in submesoscale cold filaments off Peru.

NASA Astrophysics Data System (ADS)

Thomsen, Soeren; Kanzow, Torsten; Colas, Francois; Echevin, Vincent; Krahmann, Gerd

2015-04-01

The Peruvian upwelling regime is characterized by pronounced submesoscale variability including filaments and sharp density fronts. Submesoscale frontal processes can drive large vertical velocities and enhance vertical tracer fluxes in the upper ocean. The associated high temporal and spatial variability poses a large challenge to observational approaches targeting submesoscale processes. In this study the role of submesoscale processes for both the ventilation of the near-coastal oxygen minimum zone off Peru and the physical-biogeochemical coupling at these scales is investigated. For our study we use satellite based sea surface temperature measurements in combination with multiple high-resolution glider observations of temperature, salinity, oxygen and chlorophyll fluorescence carried out in January and February 2013 off Peru near 14°S during active upwelling. Additionally, high-resolution regional ocean circulation model outputs (ROMS) are analysed. At the beginning of our observations a previously upwelled, productive and highly oxygenated body of water is found within the mixed layer. Subsequently, a cold filament forms and the waters are moved offshore. After the decay of the filament and the relaxation of the upwelling front, the oxygen enriched surface water is found within the previously less oxygenated thermocline suggesting the occurrence of frontal subduction. A numerical model simulation is used to analyse the evolution of passive tracers and Lagrangian floats within several upwelling filaments, whose vertical structure and hydrographic properties agree well with the observations. The simulated temporal evolution of the tracers and floats support our interpretation that the subduction of previously upwelled water indeed occurs within cold filaments off Peru. Filaments are common features within eastern boundary upwelling systems, which all encompass large oxygen minimum zones. However, most state of-the-art large and regional scale physical-biogeochemical ocean models do not resolve submesoscale filaments and the associated downward transport of oxygen and other solutes. Even if the observed subduction event only reaches into the still oxygenated thermocline the associated ventilation mechanism likely influences the shape and depth of the upper boundary of oxygen minimum zones, which would probably be even shallower without this process.

Inferring Source Regions and Supply Mechanisms of Iron in the Southern Ocean from Satellite Data

NASA Astrophysics Data System (ADS)

Graham, R. M.

2016-02-01

In many biogeochemical models a large shelf sediment iron flux is prescribed through the seafloor over all areas of bathymetry shallower than 1000 m. Here we infer the likely location of shelf sediment iron sources by identifying where mean annual satellite chlorophyll concentrations are enhanced over shallow bathymetry ( < 1000 m). We show that mean annual chlorophyll concentrations are not visibly enhanced over areas of shallow bathymetry located more than 500 km from a coastline. Chlorophyll concentrations > 2 mg m-3are only found within 50 km of a continental or island coastline. These results suggest that large sedimentary iron fluxes only exist on continental or island shelves. Large sedimentary iron fluxes are unlikely to be found on isolated seamounts and submerged plateaus. We further compare satellite chlorophyll concentrations to the position of ocean fronts to assess the relative role of horizontal advection and upwelling for supplying iron to the ocean surface. Sharp gradients in chlorophyll concentrations are observed across western boundary currents. Large chlorophyll blooms develop where western boundary currents detach from the continental shelves and turn eastwards into the Southern Ocean. Chlorophyll concentrations are enhanced along contours of sea surface height extending off continental and island shelves. These observations support the hypothesis that bioavailable iron from continental shelves is entrained into western boundary currents and advected into the Sub-Antarctic Zone along the Dynamical Subtropical Front. Likewise, iron from island shelves is entrained into nearby fronts and advected downstream. Mean annual chlorophyll concentrations are very low in open ocean regions with large modelled upwelling velocities, where fronts cross over topographic ridges. These results suggests that open ocean upwelling is unlikely to deliver iron to the surface from deep sources such as hydrothermal vents.

Dynamics of Black Band Disease in a Diploria strigosa population subjected to annual upwelling on the northeastern coast of Venezuela

NASA Astrophysics Data System (ADS)

Rodríguez, S.; Cróquer, A.

2008-06-01

Temporal variability of Black Band Disease (BBD) prevalence, incidence, recurrence, recovery and virulence was estimated in a Diploria strigosa population from an upwelling zone of Venezuela, for 1 year between August 2004 and August 2005. The sampling spanned both upwelling and non-upwelling seasons, and included three samplings, roughly 60 days apart, within each season. The negative effects of BBD epizootiology in the sampling population (El Mercado reef) were positively correlated with sea surface temperature (taken as an upwelling estimator). Disease prevalence, incidence and recurrence decreased significantly during upwelling, and the recovery rate increased. Contrary to expectations, tissue mortality did not decrease significantly during the upwelling season, remaining at 1.2 ± 0.7 mm day-1. BBD prevalence, and the ensuing rates of tissue mortality were higher than values previously reported for other Caribbean reefs, even during upwelling episodes, suggesting that nutrient enrichment of the local waters by upwelling counteracts the expected reductions of the disease prevalence and virulence due to the lower temperature. Colonies which had previously been infected with BBD were up to six times more susceptible to new infections than those which were not infected during the preceding 7 months, suggesting that the infected colonies never healed completely. The high variability between tissue mortality values among coral colonies also suggests that overall host health-status may alter susceptibility to BBD infections.

Coupled ice-ocean dynamics in the marginal ice zones Upwelling/downwelling and eddy generation

NASA Technical Reports Server (NTRS)

Hakkinen, S.

1986-01-01

This study is aimed at modeling mesoscale processes such as upwelling/downwelling and ice edge eddies in the marginal ice zones. A two-dimensional coupled ice-ocean model is used for the study. The ice model is coupled to the reduced gravity ocean model through interfacial stresses. The parameters of the ocean model were chosen so that the dynamics would be nonlinear. The model was tested by studying the dynamics of upwelling. Wings parallel to the ice edge with the ice on the right produce upwelling because the air-ice momentum flux is much greater than air-ocean momentum flux; thus the Ekman transport is greater than the ice than in the open water. The stability of the upwelling and downwelling jets is discussed. The downwelling jet is found to be far more unstable than the upwelling jet because the upwelling jet is stabilized by the divergence. The constant wind field exerted on a varying ice cover will generate vorticity leading to enhanced upwelling/downwelling regions, i.e., wind-forced vortices. Steepening and strengthening of vortices are provided by the nonlinear terms. When forcing is time-varying, the advection terms will also redistribute the vorticity. The wind reversals will separate the vortices from the ice edge, so that the upwelling enhancements are pushed to the open ocean and the downwelling enhancements are pushed underneath the ice.

Seasonal variation of the South Indian tropical gyre

NASA Astrophysics Data System (ADS)

Aguiar-González, Borja; Ponsoni, Leandro; Ridderinkhof, Herman; van Aken, Hendrik M.; de Ruijter, Will P. M.; Maas, Leo R. M.

2016-04-01

The South Indian tropical gyre receives and redistributes water masses from the Indonesian Throughflow (ITF), a source of Pacific Ocean water which represents the only low-latitude connector between the world oceans and, therefore, a key component in the global ocean circulation and climate system. We investigate the seasonal variation of the South Indian tropical gyre and its associated open-ocean upwelling system, known as the Seychelles-Chagos Thermocline Ridge (SCTR), based on satellite altimeter data (AVISO) and global atlases of temperature and salinity (CARS09), wind stress (SCOW) and wind-driven circulation. Two novel large-scale features governing the upper geostrophic circulation of the South Indian tropical gyre are revealed. First, the seasonal shrinkage of the ocean gyre. This occurs when the South Equatorial Countercurrent (SECC) recirculates before arrival to Sumatra from winter to spring, in apparent synchronization with the annual cycle of the ITF. Second, the open-ocean upwelling is found to vary following seasonality of the overlying geostrophic ocean gyre, a relationship that has not been previously shown for this region. An analysis of major forcing mechanisms suggests that the thermocline ridge results from the constructive interaction of basin-scale wind stress curl, local-scale wind stress forcing and remote forcing driven by Rossby waves of different periodicity: semiannual in the west, under the strong influence of monsoonal winds; and, annual in the east, where the southeasterlies prevail. One exception occurs during winter, when the well-known westward intensification of the upwelling core, the Seychelles Dome, is shown to be largely a response of the wind-driven circulation. Broadly speaking, the seasonal shrinkage of the ocean gyre (and the SCTR) is the one feature that differs most when the geostrophic circulation is compared to the wind-driven Sverdrup circulation. From late autumn to spring, the eastward SECC recirculates early in the east on feeding the westward South Equatorial Current, therefore closing the gyre before arrival to Sumatra. We find this recirculation longitude migrates over 20° and collocates with the westward advance of a zonal thermohaline front emerging from the encounter between (upwelled) Indian Equatorial Water and relatively warmer and fresher Indonesian Throughflow Water. We suggest this front, which we call the Indonesian Throughflow Front, plays an important role as forcing to the tropical gyre, generating southward geostrophic flows that contribute to the early recirculation of the SECC at longitudes more westward than predicted from the barotropic wind-driven circulation. Because our findings are based on time-averaged seasonal fields from 22 years of satellite altimeter data and from about 60 years of non-systematic sampling of ocean temperature and salinity data (CARS09), we stress the importance of further study on the possibility that interanual variability in the seasonal ITF may cause changes in the seasonal resizing of the ocean gyre and its associated upwelling ridge.

A study on the seasonal variability of upwelling and its effects on physical parameters in Arabian Sea

NASA Astrophysics Data System (ADS)

Shukla, Rohit Kumar; Shaji, Chithra; Ojha, Satya P.; Kumar, Pankaj

2017-04-01

The upwelling in Arabian Sea is an important phenomenon, mainly occurring along the southwest coast of India during summer monsoon, which increases the biological productivity in the region. The south west coast of Arabian sea region accounts for about 53% of fish yield of the total fish production in Arabian Sea, thus it is imperative to study and understand the process of upwelling in this region. To study the upwelling features in southwest coast of India, monthly Ekman mass transport is estimated using analyzed wind and derived products from Oceansat-II scatterometer data. Seasonal variability of Ekman mass transport has been analyzed to study the occurrences of coastal upwelling in this region. Results show prominent region of upwelling along southwest coast of India is between 7° and 15° N. Transport estimate demonstrate that the strong offshore Ekman mass transport, as high as -2000 kg/m/s, was observed during summer monsoon months due to favorable wind conditions. Very weak offshore transport, as low as -200 kg/m/s, was observed during pre-monsoon months as winds were weak and spatially variable. Moderate offshore transport, up to -750 kg/m/s, was observed during winter monsoon months. The upwelling associated ocean surface features such as Sea-surface temperature (SST, from AVHRR), chlorophyll concentration (AQUA-MODIS), wind stress curl derived from Oceansat-II and sea surface salinity (SSS, from Aquarius) were examined to demonstrate the spatial and temporal evolution of upwelling in this region. With the advancement of the summer monsoon and upwelling, the monthly mean SST range reaches up to 26-27°C (August - September) from about 29-30°C (April - May). The monthly mean Chlorophyll concentration reaches up to 25-30 mg/m3 (August-September) from 0.1-0.2 mg/m3 (January-February). The monthly SSS which was observed to be about 34 psu (December 2102- January 2013) reaches to 36.5 psu (August-September). Analysis of SST from different sources suggests that the occurrence of a mini-cold pool (MCP) off the southern tip of India (STI) is a persistent phenomenon which occurs during both the summer and the winter monsoon seasons. The dynamics which governs the occurrence of MCP during the summer monsoon season is mainly due to upwelling, advection of the cold upwelled water from the western Arabian Sea and the southwest coast of India. Since, Somalia upwelling is an established fact, hence, we estimate upwelling only on southwest coast of India to understand the genesis of MCP. Results show that the genesis of MCP off STI starts by June and peaks in August and the SST attains a value as low as 26.0 °C, essentially due to upwelling and advection of upwelled water from the Somalia region along with upwelled water from southwest coast of India.

Opening Pandora's Box: The impact of open system modeling on interpretations of anoxia

NASA Astrophysics Data System (ADS)

Hotinski, Roberta M.; Kump, Lee R.; Najjar, Raymond G.

2000-06-01

The geologic record preserves evidence that vast regions of ancient oceans were once anoxic, with oxygen levels too low to sustain animal life. Because anoxic conditions have been postulated to foster deposition of petroleum source rocks and have been implicated as a kill mechanism in extinction events, the genesis of such anoxia has been an area of intense study. Most previous models of ocean oxygen cycling proposed, however, have either been qualitative or used closed-system approaches. We reexamine the question of anoxia in open-system box models in order to test the applicability of closed-system results over long timescales and find that open and closed-system modeling results may differ significantly on both short and long timescales. We also compare a scenario with basinwide diffuse upwelling (a three-box model) to a model with upwelling concentrated in the Southern Ocean (a four-box model). While a three-box modeling approach shows that only changes in high-latitude convective mixing rate and character of deepwater sources are likely to cause anoxia, four-box model experiments indicate that slowing of thermohaline circulation, a reduction in wind-driven upwelling, and changes in high-latitude export production may also cause dysoxia or anoxia in part of the deep ocean on long timescales. These results suggest that box models must capture the open-system and vertically stratified nature of the ocean to allow meaningful interpretations of long-lived episodes of anoxia.

Visible to Near-infrared Spectral Reflectance, NGEE-Arctic Tram, Barrow, Alaska, 2015-2017

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meng, Ran; McMahon, Andrew; Rogers, Alistair

Canopy spectral reflectance collected from the NGEE-Arctic automated tram platform using a PP-Systems UniSpec-DC spectrometer. Downwelling radiance was measured using a 2 meter fiber optic cable connected to a cosine diffuser. Upwelling (i.e. reflected) radiance was measured using a 2 meter cable connected to a 12 degree field-of-view (FOV) lens. Canopy reflectance was calculated using the ratio of upwelling to downwelling radiance measured over a 99.99% reflectance Spectralon standard measured at the start of each measurement set.

Late Pliocene Sea Surface Temperature contrast in the Benguela upwelling as recorded by foraminiferal Mg/Ca and alkenones

NASA Astrophysics Data System (ADS)

Leduc, G.; Garbe-Schoenberg, C.; Regenberg, M.; Schneider, R. R.

2011-12-01

Alkenone-based sea surface temperature (SST) in the Benguela region reveal quite warm and stable conditions between ~3.0 and 2.0 Ma, coinciding with a period of very high diatom production as revealed by mass accumulation rates (MAR) of biogenic opal (Marlow et al., 2000, Science; Etourneau et al., 2009, Geology). Such a pattern is difficult to believe with the general perception that high diatom productivity results from strong coastal upwelling associated with pronounced Surface Ocean cooling. Therefore we assessed whether different paleothermometers from the same sedimentary archive (i.e. ODP site 1082) provide different results for the Namibian upwelling system by performing a comparison between alkenone-derived temperatures and those from the planktonic foraminifera Globigerinoides bulloides, a species known to proliferate in upwelling regions. We used laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for multiple in situ determination of Mg/Ca in single tests of G. bulloides. These measurements allow monitoring of contaminant phases linked to Mg-rich clays (monitored by Al/Ca) and Mn-rich foraminiferal tests, which contain substantial high Mg (monitored by Mn/Ca) (Pena et al., 2005, G-cubed). Moreover, using LA-ICP-MS measurements for Mg/Ca ratios on single specimens allows estimating the range of seasonal or vertical temperature variability by considering the intra-sample variance in the SST estimated from different specimens and/or different chambers within the same specimen. When compared to the Pliocene alkenone SST record, the Mg/Ca-ratios imply SSTs colder by ~10°C. A similar contrast in SST estimates between these two proxies was reported for the last 20 ka in the same region (Farmer et al., 2005, Paleoceanography). Such discrepancy can be reconciled by assuming that the two SST proxies are either strongly skewed towards warm (non-upwelling) and cold (upwelling) conditions for alkenones and Mg/Ca SST, respectively, or by the possibility that G. bulloides captures a temperature signal integrated over a larger water depth range. If representative for a specific season, downcore SST estimates from the two proxies may provide reliable evidences for changes in the seasonal temperature contrasts and thus upwelling intensity during the Pliocene. Even if the absolute temperature contrasts recorded between these two proxies have not dramatically changed between the Pliocene and Late Quaternary, the range of SST estimates between single specimen Mg/Ca values may hint to changes in past upwelling intensity. Accordingly, the scattering of intra-sample Mg/Ca values tends to increase together with the opal MAR, probably reflecting enhanced temperature contrasts at times of intense upwelling and diatom production which occurred during the cold season, one feature that is not captured by alkenone SST records.

Changes in monsoon-driven upwelling in the South China Sea over glacial Terminations I and II: a multi-proxy record

NASA Astrophysics Data System (ADS)

Sadatzki, Henrik; Sarnthein, Michael; Andersen, Nils

2016-06-01

Upwelling intensity in the South China Sea has changed over glacial-interglacial cycles in response to orbital-scale changes in the East Asian Monsoon. Here, we evaluate new multi-proxy records of two sediment cores from the north-eastern South China Sea to uncover millennial-scale changes in winter monsoon-driven upwelling over glacial Terminations I and II. On the basis of U/Th-based speleothem chronology, we compare these changes with sediment records of summer monsoon-driven upwelling east of South Vietnam. Ocean upwelling is traced by reduced (UK'37-based) temperature and increased nutrient and productivity estimates of sea surface waters (δ13C on planktic foraminifera, accumulation rates of alkenones, chlorins, and total organic carbon). Accordingly, strong winter upwelling occurred north-west of Luzon (Philippines) during late Marine Isotope Stage 6.2, Heinrich (HS) and Greenland stadials (GS) HS-11, GS-26, GS-25, HS-1, and the Younger Dryas. During these stadials, summer upwelling decreased off South Vietnam and sea surface salinity reached a maximum suggesting a drop in monsoon rains, concurrent with speleothem records of aridity in China. In harmony with a stadial-to-interstadial see-saw pattern, winter upwelling off Luzon in turn was weak during interstadials, in particular those of glacial Terminations I and II, when summer upwelling culminated east of South Vietnam. Most likely, this upwelling terminated widespread deep-water stratification, coeval with the deglacial rise in atmospheric CO2. Yet, a synchronous maximum in precipitation fostered estuarine overturning circulation in the South China Sea, in particular as long as the Borneo Strait was closed when sea level dropped below -40 m.

A numerical analysis of shipboard and coastal zone color scanner time series of new production within Gulf Stream cyclonic eddies in the South Atlantic Bight

NASA Technical Reports Server (NTRS)

Pribble, J. Raymond; Walsh, John J.; Dieterle, Dwight A.; Mueller-Karger, Frank E.

1994-01-01

Eddy-induced upwelling occurs along the western edge of the Gulf Stream between Cape Canaveral, Florida, and Cape Hatteras, North Carolina, in the South Atlantic Bight (SAB). Coastal zone color scanner images of 1-km resolution spanning the period April 13-21, 1979, were processed to examine these eddy features in relation to concurrent shipboard and current/temperature measurements at moored arrays. A quasi-one-dimensional (z), time dependent biological model, using only nitrate as a nutrient source, has been combined with a three-dimensional physical model in an attempt to replicate the observed phytoplankton field at the northward edge of an eddy. The model is applicable only to the SAB south of the Charleston Bump, at approximately 31.5 deg N, since no feature analogous to the bump exists in the model bathymetry. The modeled chlorophyll, nitrate, and primary production fields of the euphotic zone are very similar to those obtained from the satellite and shipboard data at the leading edges of the observed eddies south of the Charleston Bump. The horizontal and vertical simulated fluxes of nitrate and chlorophyll show that only approximately 10% of the upwelled nitrate is utilized by the phytoplankton of the modeled grid box on the northern edge of the cyclone, while approximately 75% is lost horizontally, with the remainder still in the euphotic zone after the 10-day period of the model. Loss of chlorophyll due to sinking is very small in this strong upwelling region of the cyclone. The model is relatively insensitive to variations in the sinking parameterization and the external nitrate and chlorophyll fields but is very sensitive to a reduction of the maximum potential growth rate to half that measured. Given the success of this model in simulating the new production of the selcted upwelling region, other upwelling regions for which measurements or successful models of physical and biological quantities and rates exist could be modeled similarly.

Linking the Modern and Recent Record of Cabo Frio Upwelling with Local Climate and Biogeochemical Processes in Hypersaline Coastal Lagoons, Região dos Lagos, Rio de Janeiro, Brazil

NASA Astrophysics Data System (ADS)

McKenzie, J. A.; Nascimento, G. S.; Albuquerque, A. L.; Belem, A. L.; Carreira, R.; Eglinton, T. I.; Vasconcelos, C.

2015-12-01

A unique marine and lagoonal system along the coast east of Rio de Janeiro is being investigated to understand the impact of climatic variability on the South Atlantic carbon cycle and biomineralisation processes involved in carbonate precipitation in the hypersaline coastal lagoons. The region is dominated by a semi-arid microclimate attributed to the local coastal upwelling phenomenon near Cabo Frio. The intensity of the upwelling affects the hydrology of the annual water and biogeochemical cycles in the lagoons, as well as biogeochemical signals of environmental change recorded in both onshore and offshore sediments. Preliminary results of δ18O and δD values of water samples collected monthly in Lagoa Vermelha and Brejo do Espinho from 2011 to 2014 show lower values for waters corresponding to the wet season, reflecting increased input of meteoric water. The higher values for waters collected during the dry season reflect the greater amount of evaporation with increased seasonal aridity. Radiocarbon dating of Holocene marine and lagoonal cores indicates that Mg-carbonate precipitation in the lagoons is associated with high evaporation. Modern field observations for the last 3 years suggest that the amount of carbonate precipitation is correlated with evaporitic conditions associated with the upwelling phenomenon. A calibration study of hydrogen isotopic fractionation in the modern lagoons is underway to define a relationship between δDlipid of suspended particles and δDwater of associated water. This isotopic relationship will be applied to material obtained in cores from the lagoons. Offshore cores will be studied using well-tested paleotemperature proxies to evaluate the intensity of the upwelling during the Holocene. In summary, linking the coastal upwelling with the lagoonal hydrology has the potential to furnish important insights about the relationship between the local climate and paleoceanographic circulation associated with the regional carbon cycle.

Upwelling Measurement Issues at the CERES Ocean Validation Experiment (COVE)

NASA Astrophysics Data System (ADS)

Fabbri, B. E.; Schuster, G. L.; Denn, F. M.; Arduini, R. F.; Madigan, J. J.; Rutan, D. A.

2016-12-01

The Clouds and the Earth's Radiant Energy System (CERES) satellite measures both solar-reflected and Earth-emitted radiation from the Earth's surface to the top of the atmosphere. One surface validation site is located at Chesapeake Light Station, approximately 25 kilometers east of Virginia Beach, Virginia (coordinates: 36.90N, 75.71W). In 1999, the CERES Ocean Validation Experiment (COVE) was established at Chesapeake Light Station. COVE is in its 17th year collecting radiometric and meteorological data. Other measurements over this time period include aerosol optical depth, water leaving radiance, precipitable water vapor and more. The issues we are trying to resolve for the upwelling flux are two-fold. First, there is the "shadow effect". In the morning, the shadow of the tower appears on the water in the field of view underneath the shortwave (SW) and longwave (LW) upwelling instruments. An attempt to understand the shading effect is made by separating the data into "shaded" and "unshaded" time periods using the Solar Azimuth (SA) angle. SA < 180 degrees are considered shaded, and SA > 180 degrees are considered unshaded. Upwelling SW shaded and unshaded datasets differ by a maximum of 9.5 W/m2 and a minimum of -0.7 W/m2 with the delta mean resulting in 3.6 W/m2. Upwelling LW shaded and unshaded datasets differ by a maximum of 8.0 W/m2 and a minimum of 1.0 W/m2 with the delta mean resulting in 3.7 W/m2. The second issue is the "tower radiating effect" which is especially noticeable on clear, sunny days. During these days, the tower tends to heat up and radiate extra heat energy that is measured by the LW instrument. We compare Infrared Radiation Thermometer (IRT) measurements to Precision Infrared Radiometer (PIR) measurements and make a case for using IRT measurements as upwelling LW.

Characterization of the structure and cross-shore transport properties of a coastal upwelling filament using three-dimensional finite-size Lyapunov exponents

NASA Astrophysics Data System (ADS)

Bettencourt, João. H.; Rossi, Vincent; Hernández-García, Emilio; Marta-Almeida, Martinho; López, Cristóbal

2017-09-01

The three-dimensional structure, dynamics, and dispersion characteristics of a simulated upwelling filament in the Iberian upwelling system are analyzed using Lagrangian tools. We used a realistic regional simulation of the western Iberian shelf which is concomitant with an in situ oceanographic campaign that surveyed the area. We compute 3-D fields of finite-size Lyapunov exponents (FSLE) from 3-D velocity fields and extract the field's ridges to study the spatial distribution and temporal evolution of the Lagrangian Coherent Structures (LCSs) evolving around the filament. We find that the most intense curtain-like LCSs delimit the boundaries of the whole filamentary structure whose general properties match well the observations. The filament interior is characterized by small dispersion of fluid elements. Furthermore, we identify a weak LCS separating the filament into a warmer vein and a colder filament associated with the interaction of a mesoscale eddy with the upwelling front. The cold upwelled water parcels move along the filament conserving their density. The filament itself is characterized by small dispersion of fluid elements in its interior. The comparison of LCSs with potential temperature and salinity gradient fields shows that the outer limits of the filament coincide with regions of large hydrographic gradients, similar to those observed, explaining the isolation of the interior of the filament with the surrounding waters. We conclude that the Lagrangian analysis used in this work is useful in explaining the dynamics of cross-shore exchanges of materials between coastal regions and the open ocean due to mesoscale processes.

The Earth's Hot Spots.

ERIC Educational Resources Information Center

Vink, Gregory E.; And Others

1985-01-01

Hot spots are isolated areas of geologic activity where volcanic eruptions, earthquakes, and upwelling currents occur far from plate boundaries. These mantle plumes are relatively stable and crustal plates drift over them. The nature and location of hot spots (with particular attention to the Hawaiian Islands and Iceland) are discussed. (DH)

Biological and physical oceanographic observations pertaining to the trawl fishery in a region of persistent coastal upwelling

NASA Technical Reports Server (NTRS)

Howe, J. T.; Gibson, D. B.; Evans, T. O.; Breaker, L.; Wrigley, R. C.; Broenkow, W. W.

1981-01-01

An upwelling episode in the Point Sal region of the central California coast is examined by using data obtained by a data buoy. The episodes was interrupted by the abrupt abatement of the strong wind which promotes coastal upwelling. The mean hourly upwelling index is calculated to be higher than the 20 year mean monthly value. During 3 days of light wind commercial bottom trawl operations were possible. Shipboard estimates of chlorophyll content in surface waters during trawling show the high concentrations that are indicative of a rich biomass of phytoplankton, a result of the upwelling episode. Satellite imagery shows the extent of the upwelling water to be of the order of 100 km offshore; the result of many upwelling episodes. Shipboard echo sounder data show the presence of various delmersal species and of zooplakton; the latter graze on the phytoplankton in the upper euphotic layers. The fish catch data are recorded according to species for 2 days of trawling, and the catch per trawl hour is recorded.

Holocene sedimentation processes and environmental changes along the Namibian coastline

NASA Astrophysics Data System (ADS)

Schüller, Irka; Belz, Lukas; Wilkes, Heinz; Wehrmann, Achim

2016-04-01

The regional oceanic and atmospheric circulation patterns strongly control environmental conditions in southern Africa. Changes in the system may have significant consequences on climate and related processes. The hyper arid coast of Namibia is mainly influenced by (1) the cold Benguela upwelling, (2) the Benguela current and (3) the Angola current. The Benguela current transports the cool, upwelling water from south to north and interacts with the warm, contrary flowing Angola current at the Angola-Benguela Front (ABF). Today the ABF is located around the Namibian-Angolan border with minor seasonal changes. Therefore, climate and environment at the Namibian coast are affected by the cold water conditions. It is known evidently that the location of the ABF changed during the Holocene over several latitudes and enabled warm water species to expand their range farther south. Several (paleo-) lagoons (coastal salt pans) exist along the Namibian coastline. Most of them are already barred and filled by longshore sediment transport processes. Tidal flooding and active sedimentation processes are restricted to the southernmost lagoons. Two different types of sediments occur. The northern pans contain well sorted, siliciclastic medium sands. Fine-layered alternation refers to changes in mineral composition. The southern pans are dominated by typical tidal sediments with a high amount of benthic fauna (mainly bivalves and gastropods). At Cape Cross the distinct shift between both facies is documented in the cores. Age determinations of core material prove a very fast sediment filling of the distinct lagoons with high sedimentation rates. However, the age of closure differs from lagoon to lagoon. Northern pan sediments are much older (Cape Cross: ~ 5000 a BP) than southern (Sandwich Bay and Conception Bay: 1800 - 300 a BP). Additional information are supported by river clay deposits (~ 36600 a BP) and fossil reed systems (~ 47900 a BP) in Conception Bay and peat deposits at the fossil Kuiseb delta between Walvis Bay and Sandwich Bay (~ 1350 - 750 a BP). The results of our analyses of lagoon and pan sediments as well as the fossil remnants allow the reconstruction of coastal sedimentation processes as well as the associated Holocene environmental changes at the coast and the terrestrial hinterland.

Strongly-sheared wind-forced currents in the nearshore regions of the central Southern California Bight

USGS Publications Warehouse

Noble, Marlene A.; Rosenberger, Kurt; Robertson, George L.

2015-01-01

Contrary to many previous reports, winds do drive currents along the shelf in the central portion of the Southern California Bight (SCB). Winds off Huntington Beach CA are the dominant forcing for currents over the nearshore region of the shelf (water depths less than 20 m). Winds control about 50–70% of the energy in nearshore alongshelf surface currents. The wind-driven current amplitudes are also anomalously high. For a relatively weak 1 dyne/cm2 wind stress, the alongshelf surface current amplitudes in this region can reach 80 cm/s or more. Mid-depth current amplitudes for the same wind stress are around 30–40 cm/s. These wind-driven surface current amplitudes are much larger than previously measured over other nearshore shelf regions, perhaps because this program is one of the few that measured currents within a meter of the surface. The near-bed cross-shelf currents over the nearshore region of the Huntington Beach shelf have an Ekman response to winds in that they upwell (downwell) for down (up) coast winds. This response disappears further offshore. Hence, there is upwelling in the SCB, but it does not occur across the entire shelf. Subthermocline water in the nearshore region that may contain nutrients and plankton move onshore when winds are southeastward, but subthermocline water over the shelf break is not transported to the beach. The currents over the outer shelf are not predominately controlled by winds, consistent with previous reports. Instead, they are mainly driven by cross-shelf pressure gradients that are independent of local wind stress.

Zooplankton Responses to Low-Oxygen Condition upon a Shallow Oxygen Minimum Zone in the Upwelling Region off Chile

NASA Astrophysics Data System (ADS)

Hidalgo, P.; Escribano, R.

2015-12-01

A shallow oxygen minimum zone (OMZ) is a critical component in the coastal upwelling ecosystem off Chile. This OMZ causes oxygen-deficient water entering the photic layer and affecting plankton communities having low tolerance to hypoxia. Variable, and usually species-dependent, responses of zooplankton to hypoxia condition can be found. Most dominant species avoid hypoxia by restricting their vertical distribution, while others can temporarily enter and even spent part of their life cycle within the OMZ. Whatever the case, low-oxygen conditions appear to affect virtually all vital rates of zooplankton, such as mortality, fecundity, development and growth and metabolism, and early developmental stages seem more sensitive, with significant consequences for population and community dynamics. For most study cases, these effects are negative at individual and population levels. Observations and predictions upon increasing upwelling intensity over the last 20-30 years indicate a gradual shoaling of the OMZ, and so that an expected enhancement of these negative effects of hypoxia on the zooplankton community. Unknown processes of adaptation and community-structure adjustments are expected to take place with uncertain consequences for the food web of this highly productive eastern boundary current ecosystem.

Episodic Upwelling of Zooplankton within a Bowhead Whale Feeding Area near Barrow, AK

DTIC Science & Technology

2012-09-30

during other periods (Fig. 3). Bowhead (Balaena mysticetus) and beluga ( Delphinapterus leuca ) whales are the only Arctic endemic cetaceans that...Clarke, J.T. Correlation of a strong Alaska Coastal Current with the presence of beluga whales ( Delphinapterus leucas ) near Barrow, Alaska. Marine...Stafford, K.M., Okkonen, S.R., Clarke, J.T. Correlation of a strong Alaska Coastal Current with the presence of beluga whales ( Delphinapterus

A long history of equatorial deep-water upwelling in the Pacific Ocean

NASA Astrophysics Data System (ADS)

Zhang, Yi Ge; Pagani, Mark; Henderiks, Jorijntje; Ren, Haojia

2017-06-01

Cold, nutrient- and CO2-rich waters upwelling in the eastern equatorial Pacific (EEP) give rise to the Pacific cold tongue. Quasi-periodic subsidence of the thermocline and attenuation in wind strength expressed by El Niño conditions decrease upwelling rates, increase surface-water temperatures in the EEP, and lead to changes in regional climates both near and far from the equatorial Pacific. EEP surface waters have elevated CO2 concentrations during neutral (upwelling) or La Niña (strong upwelling) conditions. In contrast, approximate air-sea CO2 equilibrium characterizes El Niño events. One hypothesis proposes that changes in physical oceanography led to the establishment of a deep tropical thermocline and expanded mixed-layer prior to 3 million years ago. These effects are argued to have substantially reduced deep-water upwelling rates in the EEP and promoted a "permanent El Niño-like" climate state. For this study, we test this supposition by reconstructing EEP "excess CO2" and upwelling history for the past 6.5 million years using the alkenone-pCO2 methodology. Contrary to previous assertions, our results indicate that average temporal conditions in the EEP over the past ∼6.5 million years were characterized by substantial CO2 disequilibrium and high nutrient delivery to surface waters - characteristics that imply strong upwelling of deep waters. Upwelling appears most vigorous between ∼6.5 to 4.5 million years ago coinciding with high accumulation rates of biogenic material during the late Miocene - early Pliocene "biogenic bloom".

Far-reaching transport of Pearl River plume water by upwelling jet in the northeastern South China Sea

NASA Astrophysics Data System (ADS)

Chen, Zhaoyun; Pan, Jiayi; Jiang, Yuwu; Lin, Hui

2017-09-01

Satellite images from the Moderate Resolution Imaging Spectroradiometer (MODIS) show that there was a belt of turbid water appearing along an upwelling front near the Chinese coast of Guangdong, and indicate that the turbid water of the Pearl River plume water could be transported to a far-reaching area east of the Taiwan Bank. Numerical modeling results are consistent with the satellite observations, and reveal that a strong jet exists at the upwelling front with a speed as high as 0.8 m s- 1, which acts as a pathway for transporting the high-turbidity plume water. The dynamical analysis suggests that geostrophic equilibrium dominates in the upwelling front and plume areas, and the baroclinicity of the upwelling front resulting from the horizontal density gradient is responsible for the generation of the strong jet, which enhances the far-reaching transport of the terrigenous nutrient-rich water of the Pearl River plume. Model sensitivity analyses also confirm that this jet persists as long as the upwelling front exists, even when the wind subsides and becomes insignificant. Further idealized numerical model experiments indicate that the formation and persistence of the upwelling front jet depend on the forcing strength of the upwelling-favorable wind. The formation time of the jet varies from 15 to 158 h as the stress of the upwelling-favorable wind changes from 0.2 to 0.01 N m- 2. With the persistent transport of the nutrient-rich plume water, biophysical activities can be promoted significantly in the far-reaching destination area of the oligotrophic water.

Short commentary on marine productivity at Arctic shelf breaks: upwelling, advection and vertical mixing

NASA Astrophysics Data System (ADS)

Randelhoff, Achim; Sundfjord, Arild

2018-04-01

The future of Arctic marine ecosystems has received increasing attention in recent years as the extent of the sea ice cover is dwindling. Although the Pacific and Atlantic inflows both import huge quantities of nutrients and plankton, they feed into the Arctic Ocean in quite diverse regions. The strongly stratified Pacific sector has a historically heavy ice cover, a shallow shelf and dominant upwelling-favourable winds, while the Atlantic sector is weakly stratified, with a dynamic ice edge and a complex bathymetry. We argue that shelf break upwelling is likely not a universal but rather a regional, albeit recurring, feature of the new Arctic. It is the regional oceanography that decides its importance through a range of diverse factors such as stratification, bathymetry and wind forcing. Teasing apart their individual contributions in different regions can only be achieved by spatially resolved time series and dedicated modelling efforts. The Northern Barents Sea shelf is an example of a region where shelf break upwelling likely does not play a dominant role, in contrast to the shallower shelves north of Alaska where ample evidence for its importance has already accumulated. Still, other factors can contribute to marked future increases in biological productivity along the Arctic shelf break. A warming inflow of nutrient-rich Atlantic Water feeds plankton at the same time as it melts the sea ice, permitting increased photosynthesis. Concurrent changes in sea ice cover and zooplankton communities advected with the boundary currents make for a complex mosaic of regulating factors that do not allow for Arctic-wide generalizations.

Ore deposits in Africa and their relation to the underlying mantle

NASA Technical Reports Server (NTRS)

Liu, H.-S.

1981-01-01

African magmatism is largely related to the tensional stress regimes of the crust which are induced by the hotter upwelling mantle rocks. These mantle rocks may provide emanating forces and thermal energy for the upward movements of primary ore bodies with fluid inclusions in the tensional stress regimes of the crust. In this paper, the Goddard Earth Gravity Model is used to calculate a detailed subcrustal stress system exerted by mantle convection under Africa. The resulting system is found to be correlated with the African metallogenic provinces. Recognition of the full spectrum of ore deposits in Africa that may be associated with the hotter upwelling mantle rocks has provided an independent evidence to support the hypothesis of mantle-derived heat source for ore deposits.

The Characteristics of Marine Environment around the Ieodo in Aug. 2016

NASA Astrophysics Data System (ADS)

Choi, E.; KIM, S. H.; KIM, E.; KIM, B. N.; CHOI, B. K.

2017-12-01

The sea area around Ieodo is analyzed from the CTD data and the S-ADCP data observed in 23 Aug. 2016. Ieodo, an underwater reef, is located 149 km southwest of Marado in Republic of Korea. It has 4 peaks and is about 4.6 meter below sea level. It stretches about 600m north to south and 750m east to west from its top. It has the same geographical characteristics as the seamount. In the sea area around Ieodo, the northward flow appeared during the ebb tide, the southward flow appeared during the flood tide. The strong stratification formed in summer seems to change the depth depending on the sea water current. The thermocline depth becomes deeper at the north of the Ieodo when the northward current flows and the upwelling flow occurs. And the thermocline depth becomes shallower at the south when the southward current flows and the downwelling flow occurs. In this way, the upwelling and downwelling seems to be according to the tide's direction. Acknowledgements This research was a part of the projects entitled "Construction of Ocean Research Stations and their application Studies, Phase 2", funded by the Ministry of Oceans and Fisheries, Korea.

Biogeochemical cycling in the ocean. Part 1: Introduction to the effects of upwelling along the west coast of North America

NASA Technical Reports Server (NTRS)

Howe, John T.

1986-01-01

Coastal upwelling is examined as it relates to the cycling of chemical species in coastal waters along the west coast of North America. The temporal and spatial features of upwelling phenomena in the Eastern boundary regions of the North Pacific Ocean are presented and discussed in terms of upwelling episodes. Climate conditions affecting upwelling include: thermal effects, wind-induced shear stress which moves surface layers, and the curl of the wind stress vector which is thought to affect the extent and nature of upwelling and the formation of offshore convergent downwelling fronts. These effects and the interaction of sunlight and upwelled nutrients which result in a biological bloom in surface waters is modeled analytically. The roles of biological and chemical species, including the effects of predation, are discussed in that context, and relevant remote sensing and in situ observations are presented. Climatological, oceanographic, biological, physical, chemical events, and processes that pertain to biogeochemical cycling are presented and described by a set of partial differential equations. Simple preliminary results are obtained and are compared with data. Thus a fairly general framework has been laid where the many facets of biogeochemical cycling in coastal upwelled waters can be examined in their relationship to one another, and to the whole, to whatever level of detail or approximation is warranted or desired.

Spatial variability of Spanish sardine (Sardinella aurita) abundance as related to the upwelling cycle off the southeastern Caribbean Sea

PubMed Central

Cárdenas, Juan José; Achury, Alina; Astor, Yrene

2017-01-01

The Sardinella aurita fishery off northeastern Venezuela, region of seasonal wind-driven coastal-upwelling, accounts for 90% of the Caribbean Sea small pelagic catch. This law-protected artisanal fishery takes place up to ~10 km offshore. The spatial distribution, number of schools, and biomass of S. aurita were studied using eight hydro-acoustic surveys (1995–1998). The study included the analysis of satellite-derived sea surface temperature and chlorophyll-a. Surveys were grouped by strong, weak, and transitional upwelling seasons. Relationships between these observations were analyzed using Generalized Additive Models. Results show that during the primary upwelling season (January-May) sardines were widely distributed in upwelling plumes that extended up to 70 km offshore. In the other hand, during the weak upwelling season (September-October) higher sardine densities were found within 10 Km off the coastal upwelling foci. The number of small pelagic schools was directly correlated with small pelagic densities; however, regardless of the season, higher numbers of small pelagic schools were always closer to the shoreline, especially during warm conditions. These two behaviors increase the availability and catchability of sardines for the artisanal fishery during the warm season, regardless of the total stock size. Using this evidence, we pose the hypothesis that the collapse of the regional S. aurita fishery in 2005 was due to a combination of stressful habitat conditions sustained since 2004. These included bottom-up factors due to food scarcity caused by weak upwelling, combined with top-down stress due to overfishing, as sardines accumulated in narrow diminished upwelling plumes located close to the coast. The increased catchability within easily accessible upwelling foci led to the demise of this biological resource, which as of 2014 had not yet recovered. Environmental conditions affecting the sardine habitat needs to be taken into account for the management of this stock. For example, during years with weak upwelling, special measures should be taken during the warm season on the second half of the year to avoid further pressure on the stock. PMID:28654685

Dehumidification of Iberia by enhanced summer upwelling

NASA Astrophysics Data System (ADS)

Miranda, P. M.; Costa, V.; Nogueira, M.; Semedo, A.

2015-12-01

Dehumidification of Iberia by enhanced summer upwelling Miranda PMA, Costa V, Semedo AIDL, Faculdade de Ciências, University of LisbonA 24-year simulation of the recent Iberian climate, using the WRF model at 9km resolution forced by ERA-Interim reanalysis (1989-2012), is analysed for the decadal evolution of the upwelling forcing coastal wind and for column integrated Precipitable water vapour (PWV). Results indicate that, unlike what was found by Bakun et al. (2009) for the Peruvian region, a statistically significant trend in the upwelling favourable (northerly) wind has been accompanied by a corresponding decrease in PWV, not only inland but also over the coastal waters. Such increase is consistent with a reinforced northerly coastal jet in the maritime boundary layer contributing to atmospheric Ekman pumping of dry continental air into the coastal region. Diagnostics of the prevalence of the Iberian thermal low following Hoinka and Castro (2003) also show a positive trend in its frequency during an extended summer period (April to September). These results are consistent with recent studies indicating an upward trend in the frequency of upwelling in SW Iberia (Alves and Miranda 2013), and may be relevant for climate change applications as an increase in coastal upwelling (Miranda et al 2013) may lead to substantial regional impacts in the subtropics. Aknowledgements: Study supported by FCT Grant RECI/GEO-MET/0380/2012Alves JMR, Miranda PMA (2013) Variability of Iberian upwelling implied by ERA-40 and ERA-Interim reanalyses, Tellus A 2013, http://dx.doi.org/10.3402/tellusa.v65i0.19245.Bakun et al (2010) Greenhouse gas, upwelling-favorable winds, and the future of coastal ocean upwelling ecosystems, Global Change Biology, doi: 10.1111/j.1365-2486.2009.02094.xHoinka KP, Castro M (2003) The Iberian Peninsula thermal low. QJRMS, 129, 1491- 1511, doi: 10.1256/qj.01.189.Miranda et al (2013) Climate change and upwelling: response of Iberian upwelling to atmospheric forcing in a regional climate scenario. Climate Dynamics, doi: 10.1007/s00382-012-1442-9.

Microplankton biomass and diversity in the Vietnamese upwelling area during SW monsoon under normal conditions and after an ENSO event

NASA Astrophysics Data System (ADS)

Loick-Wilde, Natalie; Bombar, Deniz; Doan, Hai Nhu; Nguyen, Lam Ngoc; Nguyen-Thi, Anh Mai; Voss, Maren; Dippner, Joachim W.

2017-04-01

Investigating microplankton biomass and diversity under different climatological conditions is key to the understanding of cascading effects of climate change on nutrient cycles and biological productivity. Here we have used data collected during two contrasting summers along the coast of Viet Nam to show how climatological-driven changes can have a significant influence on the distribution of microplankton communities and their biomass via its impact on nutrient concentrations in the water column. The first summer in July 2003 followed a weak El-Nino Southern Oscillation (ENSO) event and was characterized by weak coastal upwelling, in the second summer during July 2004, upwelling was normal. Very low silicate (SiO4) concentrations and SiO4:DIN ratios characterized the source water mass for upwelling in July 2004, and dynamic SiO4 to dissolved inorganic nitrogen ratios (SiO4:DIN) mainly below the Redfield-Brzezinski ratio and DIN to phosphate ratios (DIN:PO43-) below the Redfield ratio were a common feature off Viet Nam. Much higher particle concentrations and PSi/PC ratios during normal upwelling revealed major changes in the microplankton community structure among summers. Small dinoflagellates (10-20 μm) prevailed ubiquitously during reduced upwelling. During normal upwelling, the diatom Rhizosolenia sp. dominated the cell-carbon biomass in the silicate poor upwelling waters. Trichodesmium erythraeum dominated in the Mekong-influenced and nutrient depleted offshore waters, where it co-occurred with Rhizosolenia sp. Both species were directly associated with the much higher primary production (PP) and N2 fixation rates that were quantified in earlier studies, as well as with much higher diversities at these offshore sites. Along the coast, the correlation between Rhizosolenia sp. and PP rates was less clear and the factors regulating the biomass of Rhizosolenia sp. in the upwelling waters are discussed. The very low silicate concentrations in the source water mass for upwelling and the offshore deflection of the Mekong river plume likely triggered the observed ecological differences in the microplankton communities off Viet Nam in the normal upwelling season compared to the post ENSO conditions.

Interactions between trophic levels in upwelling and non-upwelling regions during summer monsoon

NASA Astrophysics Data System (ADS)

Malik, A.; Fernandes, C. E. G.; Gonsalves, M.-J. B. D.; Subina, N. S.; Mamatha, S. S.; Krishna, K.; Varik, S.; Kumari, R.; Gauns, M.; Cejoice, R. P.; Pandey, S. S.; Jineesh, V. K.; Kamaleson, A. S.; Vijayan, V.; Mukherjee, I.; Subramanyan, S.; Nair, S.; Ingole, B.; LokaBharathi, P. A.

2015-01-01

Coastal upwelling is a regular phenomenon occurring along the southwest coast of India during summer monsoon (May-September). We hypothesize that there could be a shift in environmental parameters along with changes in the network of interactions between bacteria, phytoplankton, and zooplankton in upwelling and non-upwelling regions. During cruise # 267 on FORV Sagar Sampada, water samples were analysed for environmental and biological parameters from two transects, one upwelling region off Trivandrum (TVM) (8°26‧N, 76°20‧E-8°30‧N, 76°50‧E), and the other non-upwelling region off Calicut (CLT) (11°11‧N, 75°30‧E-11°14‧N,74°54‧E), about 230 nmi to the north. Meteorological, hydrological, and nutrient profiles confirmed upwelling off TVM. Bacteria, phytoplankton and zooplankton significantly responded. Primary and bacterial productivity enhanced together with increase in the percentage of viable bacteria (TVC). Pearson's correlation analysis pointed out the differences in bacterial interactions with other trophic levels at both transects. TVC played a prominent role in trophic interactions off TVM by depending on phytoplankton for substrate (r = 0.754). This contrasted with CLT where total counts (TC) played an important role. However, most interrelationships were less pronounced. Principal component analysis (PCA) confirmed the correlation analysis and further showed that the factor loadings of the biotic and abiotic parameters differed in strength and direction in the two regions. More importantly, the processes of mineralization by bacteria and uptake by phytoplankton are obviously more coupled off TVM as evidenced by the clustering of the related parameters in the PCA biplot. Canonical correspondence analysis also complements these findings and demonstrated that the abiotic factors influenced phytoplankton and bacteria similarly at TVM but differently at CLT. The impact on the trophic interrelationships is evident by the close association between all the variables in upwelling waters. Besides, bacteria may represent a more stable element in the food web, TVC for upwelling region and TC for non-upwelling region.

Atmospheric and oceanographic research review, 1979

NASA Technical Reports Server (NTRS)

1980-01-01

Papers generated by atmospheric, oceanographic, and climatological research performed during 1979 at the Goddard Laboratory for Atmospheric Sciences are presented. The GARP/global weather research is aimed at developing techniques for the utilization and analysis of the FGGE data sets. Observing system studies were aimed at developing a GLAS TIROS N sounding retrieval system and preparing for the joint NOAA/NASA AMTS simulation study. The climate research objective is to support the development and effective utilization of space acquired data systems by developing the GLAS GCM for short range climate predictions, studies of the sensitivity of climate to boundary conditions, and predictability studies. Ocean/air interaction studies concentrated on the development of models for the prediction of upper ocean currents, temperatures, sea state, mixed layer depths, and upwelling zones, and on studies of the interactions of the atmospheric and oceanic circulation systems on time scales of a month or more.

Upwelling Dynamic Based on Satellite and INDESO Data in the Flores Sea

NASA Astrophysics Data System (ADS)

Kurniawan, Reski; Suriamihardja, D. A.; Hamzah Assegaf, Alimuddin

2018-03-01

Upwelling phenomenon is crucial to be forecasted, mainly concerning the information of potential fishery areas. Utilization of calibrated model for recorded upwelling such as INDESO gives benefit for historical result up to the present time. The aim of this study is to estimate areas and seasons of upwelling occurrences in the Flores Sea using data assimilation of satellite and modeling result. This study uses sea surface temperature, chlorophyll-a data from level 3 of MODIS image and sea surface height from satellite Jason-2 monthly for three years (2014-2016) and INDESO model data for sea surface temperature, sea surface height, and chlorophyll-a daily for three years (2014-2016). The upwelling is indicated by declining of sea surface temperature, sea surface height and increasing of chlorophyll-a. Verification is conducted by comparing the model result with recorded MODIS satellite image. The result shows that the area of southern Makassar Strait having occurrences of upwelling phenomenon every year starting in June, extended to July and August. The strongest upwelling occurred in 2015 covering more or less the area of 23,000 km2. The relation of monthly data of satellite has significantly correlated with daily data of INDESO model

Complex trophic interactions of calanoid copepods in the Benguela upwelling system

NASA Astrophysics Data System (ADS)

Schukat, Anna; Auel, Holger; Teuber, Lena; Lahajnar, Niko; Hagen, Wilhelm

2014-01-01

Life-cycle adaptations, dietary preferences and trophic levels of calanoid copepods from the northern Benguela Current off Namibia were determined via lipid classes, marker fatty acids and stable isotope analyses, respectively. Trophic levels of copepod species were compared to other zooplankton and top consumers. Lipid class analyses revealed that three of the dominant calanoid copepod species stored wax esters, four accumulated triacylglycerols and another three species were characterised by high phospholipid levels. The two biomarker approaches (via fatty acids and stable isotopes) revealed a complex pattern of trophic positions for the various copepod species, but also highlighted the dietary importance of diatoms and dinoflagellates. Calanoides carinatus and Nannocalanus minor occupied the lowest trophic level (predominantly herbivorous) corresponding to high amounts of fatty acid markers for diatoms (e.g. 16:1(n - 7)) and dinoflagellates (e.g. 18:4(n - 3)). These two copepod species represent the classical link between primary production and higher trophic levels. All other copepods belonged to secondary or even tertiary (some deep-sea copepods) consumers. The calanoid copepod species cover the entire range of δ15N ratios, as compared to δ15N ratios of all non-calanoid taxa investigated, from salps to adult fish. These data emphasise that the trophic roles of calanoid copepods are far more complex than just interlinking primary producers with pelagic fish, which should also be considered in the process of developing realistic food-web models of coastal upwelling systems.

Analysis of coastal upwelling and the production of a biomass

NASA Technical Reports Server (NTRS)

Howe, J. T.

1979-01-01

The coastal upwelling index derived from weather data is input to a set of coupled differential equations that describe the production of a biomass. The curl of the wind stress vector is discussed in the context of the physical extent of the upwelling structure. An analogy between temperature and biomass concentration in the upwelled coastal water is derived and the relationship is quantified. The use of remote satellite or airborne sensing to obtain biomass rate production coefficients is considered.

Contradictory Evidence on Wave Forcing of Tropical Upwelling in the Brewer-Dobson Circulation - A Suggested Resolution

NASA Technical Reports Server (NTRS)

Zhou, Tiehan; Geller, Marvin A.; Lin, Wuyin

2011-01-01

ERA-40 data are analyzed to demonstrate that wave forcing at lower latitudes plays a crucial role in driving the tropical upwelling portion of the Brewer-Dobson circulation. It is shown that subtropical wave forcing is correlated with tropical upwelling on both intraseasonal and interannual time scales when transient waves are taken into account, and that tropical wave forcing exerts its influence on tropical upwelling via its body force on the zonal mean flow.

Tide-related variability of TAG hydrothermal activity observed by deep-sea monitoring system and OBSH

NASA Astrophysics Data System (ADS)

Fujioka, Kantaro; Kobayashi, Kazuo; Kato, Kazuhiro; Aoki, Misumi; Mitsuzawa, Kyohiko; Kinoshita, Masataka; Nishizawa, Azusa

1997-12-01

Hydrothermal activities were monitored by an ocean bottom seismometer with hydrophone (OBSH) and a composite measuring system (Manatee) including CTD, current meter, transmission meter and cameras at a small depression on the TAG hydrothermal mound in the Mid-Atlantic Ridge. Low-frequency pressure pulses detected by the hydrophone with semi-diurnal periodicity seem to correspond to cycles of hydrothermal upflow from a small and short-lived smoker vent close to the observing site. The peaks of pressure pulses are synchronous with the maximum gradient of areal strain decrease due to tidal load release. Microearthquakes with very near epicenters occur sporadically and do not appear to be directly correlatable to hydrothermal venting. Temporal variations in bottom water temperature also have semi-diurnal periodicity but are more complicated than the pressure events. Temperatures may be affected both by upwelling of hot water and by lateral flow of the bottom current changing its directions with ocean tide.

Electrical image of passive mantle upwelling beneath the northern East Pacific Rise.

PubMed

Key, Kerry; Constable, Steven; Liu, Lijun; Pommier, Anne

2013-03-28

Melt generated by mantle upwelling is fundamental to the production of new oceanic crust at mid-ocean ridges, yet the forces controlling this process are debated. Passive-flow models predict symmetric upwelling due to viscous drag from the diverging tectonic plates, but have been challenged by geophysical observations of asymmetric upwelling that suggest anomalous mantle pressure and temperature gradients, and by observations of concentrated upwelling centres consistent with active models where buoyancy forces give rise to focused convective flow. Here we use sea-floor magnetotelluric soundings at the fast-spreading northern East Pacific Rise to image mantle electrical structure to a depth of about 160 kilometres. Our data reveal a symmetric, high-conductivity region at depths of 20-90 kilometres that is consistent with partial melting of passively upwelling mantle. The triangular region of conductive partial melt matches passive-flow predictions, suggesting that melt focusing to the ridge occurs in the porous melting region rather than along the shallower base of the thermal lithosphere. A deeper conductor observed east of the ridge at a depth of more than 100 kilometres is explained by asymmetric upwelling due to viscous coupling across two nearby transform faults. Significant electrical anisotropy occurs only in the shallowest mantle east of the ridge axis, where high vertical conductivity at depths of 10-20 kilometres indicates localized porous conduits. This suggests that a coincident seismic-velocity anomaly is evidence of shallow magma transport channels rather than deeper off-axis upwelling. We interpret the mantle electrical structure as evidence that plate-driven passive upwelling dominates this ridge segment, with dynamic forces being negligible.

Microplastic abundance, distribution and composition along a latitudinal gradient in the Atlantic Ocean.

PubMed

Kanhai, La Daana K; Officer, Rick; Lyashevska, Olga; Thompson, Richard C; O'Connor, Ian

2017-02-15

Microplastics in the world's oceans are a global concern due to the potential threat they pose to marine organisms. This study investigated microplastic abundance, distribution and composition in the Atlantic Ocean on a transect from the Bay of Biscay to Cape Town, South Africa. Microplastics were sampled from sub-surface waters using the underway system of the RV Polarstern. Potential microplastics were isolated from samples and FT-IR spectroscopy was used to identify polymer types. Of the particles analysed, 63% were rayon and 37% were synthetic polymers. The majority of microplastics were identified as polyesters (49%) and blends of polyamide or acrylic/polyester (43%). Overall, fibres (94%) were predominant. Average microplastic abundance in the Atlantic Ocean was 1.15±1.45particlesm -3 . Of the 76 samples, 14 were from the Benguela upwelling and there was no statistically significant difference in microplastic abundance between upwelled and non-upwelled sites. Copyright © 2016 Elsevier Ltd. All rights reserved.

Dynamics of upwelling annual cycle in the equatorial Atlantic Ocean

NASA Astrophysics Data System (ADS)

Wang, Li-Chiao; Jin, Fei-Fei; Wu, Chau-Ron; Hsu, Huang-Hsiung

2017-04-01

The annual upwelling is an important component of the equatorial Atlantic annual cycle. A simple theory is proposed using the framework of Zebiak-Cane (ZC) ocean model for insights into the dynamics of the upwelling annual cycle. It is demonstrated that in the Atlantic equatorial region this upwelling is dominated by Ekman processing in the west, whereas in the east it is primarily owing to shoaling and deepening of the thermocline resulting from equatorial mass meridional recharge/discharge and zonal redistribution processes associated with wind-driven equatorial ocean waves. This wind-driven wave upwelling plays an important role in the development of the annual cycle in the sea surface temperature of the cold tongue in the eastern equatorial Atlantic.

Record of the Pacific Large Low Shear Velocity Province Upwellings Preserved in the Cretaceous Large Igneous Provinces

NASA Astrophysics Data System (ADS)

Madrigal, P.; Gazel, E.; Flores, K. E.; Bizimis, M.; Jicha, B. R.

2015-12-01

As the surface expression of deep mantle dynamics, Large Igneous Provinces (LIPs) are associated with the edges of large low shear velocity provinces (LLSVP) rooted at the core-mantle boundary. Instabilities in the LLSVP can cause periodic upwellings of material in the form of mantle plumes, which impact the lithosphere forming LIPs. However, the time frames of these massive lava outpourings are still uncertain. While continental LIPs are more readily accessible, oceanic LIPs have only been studied through drilling and sampling of fragments accreted to continental margins or island arcs, hence, they are relatively less understood. The impact of oceanic LIPs on oceanic biota is conspicuously recorded in global occurrences of black shale deposits that evidence episodes of anoxia and mass extinctions shortly after the formation of LIPs that ultimately can affect life on the entire planet. Our new geochemical and geochronological data of accreted Pacific LIPs found in the coasts of Nicoya Peninsula in Costa Rica record three LIP pulses possibly reflecting upwelling periods of the LLSVP at 140, 120 and 90 Ma. In order to test different models of origin of these LIPS, we created a complete reconstruction of the Pacific Plate configuration from the Mid-Jurassic to Upper-Cretaceous to show the existing correlation between upwelling pulses at edges of the Pacific LLSVP, oceanic anoxic events and the age from Pacific LIPs. We propose that since the formation of the Pacific plate at circa 175-180 Ma, a series of upwellings that interacted with mid-ocean ridge systems separated by 10-20 Ma have affected the planet periodically forming oceanic LIPs that still can be found today on the Pacific seafloor and accreted along the plate margins.

Alkaline phosphatase activity at the southwest coast of India: A comparison of locations differently affected by upwelling

NASA Astrophysics Data System (ADS)

Mamatha, S. S.; Malik, Ashish; Varik, Sandesh; Parvathi, V.; Jineesh, V. K.; Gauns, Mangesh U.; LokaBharathi, P. A.

2015-01-01

The realization of the potential importance of phosphorus (P) as a limiting nutrient in marine ecosystem is increasing globally. Hence, the contribution of biotic variables in mobilizing this nutrient would be relevant especially in productive coastal waters. As alkaline phosphatase activity (APA) indicates the status of P for primary production in aquatic environments, we asked the following question: is the level of APA indicative of P sufficiency or deficiency in coastal waters, especially, where upwelling is a regular phenomenon? Therefore, we have examined the total APA, chlorophyll a along with phosphatase producing bacteria (PPB) and related environmental parameters from nearshore to offshore in coastal waters off Trivandrum and Kochi regions differently affected by upwelling during the onset of monsoon. Off Trivandrum, APA in the offshore waters of 5-m layer at 2.23 μM P h- 1 was > 4 times higher than nearshore. Thus, low APA could be indicative of P sufficiency in coastal waters and higher activity suggestive of deficiency in offshore waters off Trivandrum. In contrast, there was less difference in APA between near and offshore surface waters off Kochi. Our results show that the regions differently affected by upwelling respond differently according to ambient P concentration, distance from shore or depth of water. These observations could apparently be applicable to other coastal systems as well, where gradients in upwelling and phosphate runoff have been noticed. Further studies on other transects would throw more light on the extent and direction of the relationship between APA and ambient P concentration. Such studies would help in understanding the level of control of this nutrient on the productivity of coastal waters.

Multiple mantle upwellings in the transition zone beneath the northern East-African Rift system from relative P-wave travel-time tomography

NASA Astrophysics Data System (ADS)

Civiero, Chiara; Hammond, James O. S.; Goes, Saskia; Fishwick, Stewart; Ahmed, Abdulhakim; Ayele, Atalay; Doubre, Cecile; Goitom, Berhe; Keir, Derek; Kendall, J.-Michael; Leroy, Sylvie; Ogubazghi, Ghebrebrhan; Rümpker, Georg; Stuart, Graham W.

2015-09-01

Mantle plumes and consequent plate extension have been invoked as the likely cause of East African Rift volcanism. However, the nature of mantle upwelling is debated, with proposed configurations ranging from a single broad plume connected to the large low-shear-velocity province beneath Southern Africa, the so-called African Superplume, to multiple lower-mantle sources along the rift. We present a new P-wave travel-time tomography model below the northern East-African, Red Sea, and Gulf of Aden rifts and surrounding areas. Data are from stations that span an area from Madagascar to Saudi Arabia. The aperture of the integrated data set allows us to image structures of ˜100 km length-scale down to depths of 700-800 km beneath the study region. Our images provide evidence of two clusters of low-velocity structures consisting of features with diameter of 100-200 km that extend through the transition zone, the first beneath Afar and a second just west of the Main Ethiopian Rift, a region with off-rift volcanism. Considering seismic sensitivity to temperature, we interpret these features as upwellings with excess temperatures of 100 ± 50 K. The scale of the upwellings is smaller than expected for lower mantle plume sources. This, together with the change in pattern of the low-velocity anomalies across the base of the transition zone, suggests that ponding or flow of deep-plume material below the transition zone may be spawning these upper mantle upwellings. This article was corrected on 28 SEP 2015. See the end of the full text for details.

Patterns of spatial and temporal distribution of humpback whales at the southern limit of the Southeast Pacific breeding area.

PubMed

Guidino, Chiara; Llapapasca, Miguel A; Silva, Sebastian; Alcorta, Belen; Pacheco, Aldo S

2014-01-01

Understanding the patterns of spatial and temporal distribution in threshold habitats of highly migratory and endangered species is important for understanding their habitat requirements and recovery trends. Herein, we present new data about the distribution of humpback whales (Megaptera novaeangliae) in neritic waters off the northern coast of Peru: an area that constitutes a transitional path from cold, upwelling waters to warm equatorial waters where the breeding habitat is located. Data was collected during four consecutive austral winter/spring seasons from 2010 to 2013, using whale-watching boats as platforms for research. A total of 1048 whales distributed between 487 groups were sighted. The spatial distribution of humpbacks resembled the characteristic segregation of whale groups according to their size/age class and social context in breeding habitats; mother and calf pairs were present in very shallow waters close to the coast, while dyads, trios or more whales were widely distributed from shallow to moderate depths over the continental shelf break. Sea surface temperatures (range: 18.2-25.9°C) in coastal waters were slightly colder than those closer to the oceanic realm, likely due to the influence of cold upwelled waters from the Humboldt Current system. Our results provide new evidence of the southward extension of the breeding region of humpback whales in the Southeast Pacific. Integrating this information with the knowledge from the rest of the breeding region and foraging grounds would enhance our current understanding of population dynamics and recovery trends of this species.

Patterns of Spatial and Temporal Distribution of Humpback Whales at the Southern Limit of the Southeast Pacific Breeding Area

PubMed Central

Guidino, Chiara; Llapapasca, Miguel A.; Silva, Sebastian; Alcorta, Belen; Pacheco, Aldo S.

2014-01-01

Understanding the patterns of spatial and temporal distribution in threshold habitats of highly migratory and endangered species is important for understanding their habitat requirements and recovery trends. Herein, we present new data about the distribution of humpback whales (Megaptera novaeangliae) in neritic waters off the northern coast of Peru: an area that constitutes a transitional path from cold, upwelling waters to warm equatorial waters where the breeding habitat is located. Data was collected during four consecutive austral winter/spring seasons from 2010 to 2013, using whale-watching boats as platforms for research. A total of 1048 whales distributed between 487 groups were sighted. The spatial distribution of humpbacks resembled the characteristic segregation of whale groups according to their size/age class and social context in breeding habitats; mother and calf pairs were present in very shallow waters close to the coast, while dyads, trios or more whales were widely distributed from shallow to moderate depths over the continental shelf break. Sea surface temperatures (range: 18.2–25.9°C) in coastal waters were slightly colder than those closer to the oceanic realm, likely due to the influence of cold upwelled waters from the Humboldt Current system. Our results provide new evidence of the southward extension of the breeding region of humpback whales in the Southeast Pacific. Integrating this information with the knowledge from the rest of the breeding region and foraging grounds would enhance our current understanding of population dynamics and recovery trends of this species. PMID:25391137

Initial observation of upwelling along east coast of Peninsular Malaysia musica gratis

NASA Astrophysics Data System (ADS)

Akhir, M.; Tanggang, F.

2013-12-01

There is no published evidence of upwelling in coastal area along the east coast of Peninsular Malaysia. However numbers of recent cruise data collected during the southwest monsoon found features of thermocline lifting and isolated cooler temperature water along the coast, These sign was observed along the 104°E from numbers of parallel transects. To confirm the presence of upwelling, satellite remote sensing data was used, and numerical model experiments were conducted. Cooler sea-surface temperature along the coast was observed from both in-situ and satellite data, while upward movement in the vertical profiles agreed with the location of upwelling from both in-situ and satellite data. Moreover, these data also show that the upwelled water band along the 104°E longitude stretch approximately 650 km long. Initially, southwesterly wind during this season is believed to be the important mechanism that contributed to this wind-induced Ekman upwelling. musica gratis

Coherence of river and ocean conditions along the US West Coast during storms

USGS Publications Warehouse

Kniskern, T.A.; Warrick, J.A.; Farnsworth, K.L.; Wheatcroft, R.A.; Goni, M.A.

2011-01-01

The majority of water and sediment discharge from the small, mountainous watersheds of the US West Coast occurs during and immediately following winter storms. The physical conditions (waves, currents, and winds) within and acting upon the proximal coastal ocean during these winter storms strongly influence dispersal patterns. We examined this river-ocean temporal coherence for four coastal river-shelf systems of the US West Coast (Umpqua, Eel, Salinas, and Santa Clara) to evaluate whether specific ocean conditions occur during floods that may influence coastal dispersal of sediment. Eleven years of corresponding river discharge, wind, and wave data were obtained for each river-shelf system from USGS and NOAA historical records, and each record was evaluated for seasonal and event-based patterns. Because near-bed shear stresses due to waves influence sediment resuspension and transport, we used spectral wave data to compute and evaluate wave-generated bottom-orbital velocities. The highest values of wave energy and discharge for all four systems were consistently observed between October 15 and March 15, and there were strong latitudinal patterns observed in these data with lower discharge and wave energies in the southernmost systems. During floods we observed patterns of river-ocean coherence that differed from the overall seasonal patterns. For example, downwelling winds generally prevailed during floods in the northern two systems (Umpqua and Eel), whereas winds in the southern systems (Salinas and Santa Clara) were generally downwelling before peak discharge and upwelling after peak discharge. Winds not associated with floods were generally upwelling on all four river-shelf systems. Although there are seasonal variations in river-ocean coherence, waves generally led floods in the three northern systems, while they lagged floods in the Santa Clara. Combined, these observations suggest that there are consistent river-ocean coherence patterns along the US West Coast during winter storms and that these patterns vary substantially with latitude. These results should assist with future evaluations of flood plume formation and sediment fate along this coast. ?? 2011 Elsevier Ltd.

Estuary-ocean connectivity: fast physics, slow biology.

PubMed

Raimonet, Mélanie; Cloern, James E

2017-06-01

Estuaries are connected to both land and ocean so their physical, chemical, and biological dynamics are influenced by climate patterns over watersheds and ocean basins. We explored climate-driven oceanic variability as a source of estuarine variability by comparing monthly time series of temperature and chlorophyll-a inside San Francisco Bay with those in adjacent shelf waters of the California Current System (CCS) that are strongly responsive to wind-driven upwelling. Monthly temperature fluctuations inside and outside the Bay were synchronous, but their correlations weakened with distance from the ocean. These results illustrate how variability of coastal water temperature (and associated properties such as nitrate and oxygen) propagates into estuaries through fast water exchanges that dissipate along the estuary. Unexpectedly, there was no correlation between monthly chlorophyll-a variability inside and outside the Bay. However, at the annual scale Bay chlorophyll-a was significantly correlated with the Spring Transition Index (STI) that sets biological production supporting fish recruitment in the CCS. Wind forcing of the CCS shifted in the late 1990s when the STI advanced 40 days. This shift was followed, with lags of 1-3 years, by 3- to 19-fold increased abundances of five ocean-produced demersal fish and crustaceans and 2.5-fold increase of summer chlorophyll-a in the Bay. These changes reflect a slow biological process of estuary-ocean connectivity operating through the immigration of fish and crustaceans that prey on bivalves, reduce their grazing pressure, and allow phytoplankton biomass to build. We identified clear signals of climate-mediated oceanic variability in this estuary and discovered that the response patterns vary with the process of connectivity and the timescale of ocean variability. This result has important implications for managing nutrient inputs to estuaries connected to upwelling systems, and for assessing their responses to changing patterns of upwelling timing and intensity as the planet continues to warm. © 2016 Published by John Wiley & Sons Ltd This article has been contributed to by US Government employees and their work is in the public domain in the USA.

High resolution projections for the western Iberian coastal low level jet in a changing climate

NASA Astrophysics Data System (ADS)

Soares, Pedro M. M.; Lima, Daniela C. A.; Cardoso, Rita M.; Semedo, Alvaro

2017-09-01

The Iberian coastal low-level jet (CLLJ) is one of the less studied boundary layer wind jet features in the Eastern Boundary Currents Systems (EBCS). These regions are amongst the most productive ocean ecosystems, where the atmosphere-land-ocean feedbacks, which include marine boundary layer clouds, coastal jets, upwelling and inland soil temperature and moisture, play an important role in defining the regional climate along the sub-tropical mid-latitude western coastal areas. Recently, the present climate western Iberian CLLJ properties were extensively described using a high resolution regional climate hindcast simulation. A summer maximum frequency of occurrence above 30 % was found, with mean maximum wind speeds around 15 ms-1, between 300 and 400 m heights (at the jet core). Since the 1990s the climate change impact on the EBCS is being studied, nevertheless some lack of consensus still persists regarding the evolution of upwelling and other components of the climate system in these areas. However, recently some authors have shown that changes are to be expected concerning the timing, intensity and spatial homogeneity of coastal upwelling, in response to future warming, especially at higher latitudes, namely in Iberia and Canaries. In this study, the first climate change assessment study regarding the Western Iberian CLLJ, using a high resolution (9 km) regional climate simulation, is presented. The properties of this CLLJ are studied and compared using two 30 years simulations: one historical simulation for the 1971-2000 period, and another simulation for future climate, in agreement with the RCP8.5 scenario, for the 2071-2100 period. Robust and consistent changes are found: (1) the hourly frequency of occurrence of the CLLJ is expected to increase in summer along the western Iberian coast, from mean maximum values of around 35 % to approximately 50 %; (2) the relative increase of the CLLJ frequency of occurrence is higher in the north off western Iberia; (3) the occurrence of the CLLJ covers larger areas both latitudinal and longitudinal; (4) the CLLJ season is lengthened extending to May and September; and, (5) there are shifts for higher occurrences of higher wind speeds and for the jet core to occur at higher heights.

Episodic Upwelling of Zooplankton within a Bowhead Whale Feeding Area Near Barrow, AK

DTIC Science & Technology

2013-09-30

non-copepod prey. Bowhead (Balaena mysticetus) and beluga ( Delphinapterus leuca ) whales are the only Arctic endemic cetaceans that occur...Stafford, K.M., Okkonen, S.R., Clarke, J.T. 2013. Correlation of a strong Alaska Coastal Current with the presence of beluga whales ( Delphinapterus leucas ...Stafford, K.M., Okkonen, S.R., Clarke, J.T. 2013. Correlation of a strong Alaska Coastal Current with the presence of beluga whales ( Delphinapterus

A model study of the response of hypoxia to upwelling-favorable wind on the northern Gulf of Mexico shelf

NASA Astrophysics Data System (ADS)

Feng, Yang; Fennel, Katja; Jackson, George A.; DiMarco, Steven F.; Hetland, Robert D.

2014-03-01

The hypoxic region in the northern Gulf of Mexico, one of the largest man-made hypoxic zones in the world, has received extensive scientific study and management interest. A previous statistical study has concluded that in addition to anthropogenic nitrogen loading, the observed hypoxic extent is correlated to the duration of upwelling favorable (westerly) wind without elucidating the underlying mechanism. In this study, we use a three-dimensional, coupled hydrological-biogeochemical model to mechanistically examine how variations of the hypoxic area are related to the duration of upwelling-favorable wind. We performed scenario experiments with different durations of upwelling-favorable wind using realistic winds from summer 2002 (when upwelling-favorable winds were present only for about 1 month) and summer 2009 (when upwelling-favorable conditions started early and persisted for about 2 months). While the maximum simulated hypoxic area is approximately 15,000 km2 in both cases, the evolutions of the hypoxic area and the dates when its maximum extent are reached are different. With an early start of persistently upwelling-favorable wind in 2009, the hypoxic area reached its maximum in early summer and decreased afterwards. By contrast, the hypoxic area was small in early summer of 2002 and peaked during the short period of upwelling-favorable wind in late summer. The model revealed that the wind influences the evolution of the hypoxic area by changing the vertical and horizontal distributions of the low salinity, high chlorophyll water on the shelf.

Influence of solar radiation absorbed by phytoplankton on the thermal structure and circulation of the tropical Atlantic Ocean

NASA Astrophysics Data System (ADS)

Frouin, Robert; Ueyoshi, Kyozo; Kampel, Milton

2007-09-01

Numerical experiments conducted with an ocean general ocean circulation model reveal the potential influence of solar radiation absorbed by phytoplankton on the thermal structure and currents of the Tropical Atlantic Ocean. In the model, solar radiation penetration is parameterized explicitly as a function of chlorophyll-a concentration, the major variable affecting water turbidity in the open ocean. Two types of runs are performed, a clear water (control) run with a constant minimum chlorophyll-a concentration of 0.02 mgm -3, and a turbid water (chlorophyll) run with space- and time-varying chlorophyll-a concentration from satellite data. The difference between results from the two runs yields the biological effects. In the chlorophyll run, nutrients and biology production are implicitly taken into account, even though biogeochemical processes are not explicitly included, since phytoplankton distribution, prescribed from observations, is the result of those processes. Due to phytoplankton-radiation forcing, the surface temperature is higher by 1-2 K on average annually in the region of the North Equatorial current, the Northern part of the South Equatorial current, and the Caribbean system, and by 3-4 K in the region of the Guinea current. In this region, upwelling is reduced, and heat trapped in the surface layers by phytoplankton is not easily removed. The surface temperature is lower by 1 K in the Northern region of the Benguela current, due to increased upwelling. At depth, the equatorial Atlantic is generally cooler, as well as the eastern part of the tropical basin (excluding the region of the sub-tropical gyres). The North and South equatorial currents, as well as the Equatorial undercurrent, are enhanced by as much as 3-4 cms -1, and the circulation of the subtropical gyres is increased. Pole-ward heat transport is slightly reduced North of 35°N, suggesting that phytoplankton, by increasing the horizontal return flow in the subtropical region, may exert a cooling influence on higher latitude regions. The findings indicate that biology-induced buoyancy plays a significant role, in an indirect if not direct way, in the variability of the Tropical Atlantic Ocean, with consequences on atmospheric circulation and climate.

Influences of riverine and upwelling waters on the coastal carbonate system off Central Chile and their ocean acidification implications

NASA Astrophysics Data System (ADS)

Vargas, Cristian A.; Contreras, Paulina Y.; Pérez, Claudia A.; Sobarzo, Marcus; Saldías, Gonzalo S.; Salisbury, Joe

2016-06-01

A combined data set, combining data from field campaigns and oceanographic cruises, was used to ascertain the influence of both river discharges and upwelling processes, covering spatial and temporal variation in dissolved inorganic carbon (DIC) and aragonite saturation state. This work was conducted in one of the most productive river-influenced upwelling areas in the South Pacific coasts (36°S). Additionally, further work was also conducted to ascertain the contribution of different DIC sources, influencing the dynamics of DIC along the land-ocean range. Six sampling campaigns were conducted across seven stations at the Biobío River basin, covering approximately 200 km. Three research cruises were undertaken simultaneously, covering the adjacent continental shelf, including 12 sampling stations for hydrographic measurements. Additionally, six stations were also sampled for chemical analyses, covering summer, winter, and spring conditions over 2010 and 2011. Our results evidenced that seaward extent of the river plume was more evident during the winter field campaign, when highest riverine DIC fluxes were observed. The carbonate system along the river-ocean continuum was very heterogeneous varying over spatial and temporal scales. High DIC and pCO2 were observed in river areas with larger anthropogenic effects. CO2 supersaturation at the river plume was observed during all campaigns due to the influence of low pH river waters in winter/spring and high-pCO2 upwelling waters in summer. δ13CDIC evidenced that main DIC sources along the river and river plume corresponded to the respiration of terrestrial organic matter. We have linked this natural process to the carbonate saturation on the adjacent river-influenced coastal area, suggesting that Ωaragonite undersaturation in surface/subsurface waters is largely modulated by the influence of both river discharge and coastal upwelling events in this productive coastal area. Conditions of low Ωaragonite might impact negatively physiological traits for marine organisms, such as bivalves, gastropods, and crustaceans. Therefore, local populations from river-influenced sites could be inherently more tolerant to ocean acidification than organisms living in regions with lower Ωaragonite variability.

Geodynamics of the East African Rift System ∼30 Ma ago: A stress field model

NASA Astrophysics Data System (ADS)

Min, Ge; Hou, Guiting

2018-06-01

The East African Rift System (EARS) is thought to be an intra-continental ridge that meets the Red Sea and the Gulf of Aden at the Ethiopian Afar as the failed arm of the Afar triple junction. The geodynamics of EARS is still unclear even though several models have been proposed. One model proposes that the EARS developed in a local tensile stress field derived from far-field loads because of the pushing of oceanic ridges. Alternatively, some scientists suggest that the formation of the EARS can be explained by upwelling mantle plumes beneath the lithospheric weak zone (e.g., the Pan-African suture zone). In our study, a shell model is established to consider the Earth's spherical curvature, the lithospheric heterogeneity of the African continent, and the coupling between the mantle plumes and the mid-ocean ridge. The results are calculated via the finite element method using ANSYS software and fit the geological evidence well. To discuss the effects of the different rock mechanical parameters and the boundary conditions, four comparative models are established with different parameters or boundary conditions. Model I ignores the heterogeneity of the African continent, Model II ignores mid-ocean spreading, Model III ignores the upwelling mantle plumes, and Model IV ignores both the heterogeneity of the African continent and the upwelling mantle plumes. Compared to these models is the original model that shows the best-fit results; this model indicates that the coupling of the upwelling mantle plumes and the mid-ocean ridge spreading causes the initial lithospheric breakup in Afar and East Africa. The extension direction and the separation of the EARS around the Tanzanian craton are attributed to the heterogeneity of the East African basement.

Meeting reproductive demands in a dynamic upwelling system: Foraging strategies of a pursuit-diving seabird, the marbled murrelet

USGS Publications Warehouse

Peery, M.Z.; Newman, S.H.; Storlazzi, C.D.; Beissinger, S.R.

2009-01-01

Seabirds maintain plasticity in their foraging behavior to cope with energy demands and foraging constraints that vary over the reproductive cycle, but behavioral studies comparing breeding and nonbreeding individuals are rare. Here we characterize how Marbled Murrelets (Brachyramphus marmoratus) adjust their foraging effort in response to changes in reproductive demands in an upwelling system in central California. We radio-marked 32 murrelets of known reproductive status (9 breeders, 12 potential breeders, and 11 nonbreeders) and estimated both foraging ranges and diving rates during the breeding season. Murrelets spent more time diving during upwelling than oceanographic relaxation, increased their foraging ranges as the duration of relaxation grew longer, and reduced their foraging ranges after transitions to upwelling. When not incubating, murrelets moved in a circadian pattern, spending nighttime hours resting near flyways used to reach nesting habitat and foraging during the daytime an average of 5.7 km (SD 6.7 km) from nighttime locations. Breeders foraged close to nesting habitat once they initiated nesting and nest attendance was at a maximum, and then resumed traveling longer distances following the completion of nesting. Nonbreeders had similar nighttime and daytime distributions and tended to be located farther from inland flyways. Breeders increased the amount of time they spent diving by 71-73% when they had an active nest by increasing the number of dives rather than by increasing the frequency of anaerobiosis. Thus, to meet reproductive demands during nesting, murrelets adopted a combined strategy of reducing energy expended commuting to foraging sites and increasing aerobic dive rates. ?? 2009 by The Cooper Ornithological Society. All rights reserved.

Distribution of biogenic silica and quartz in recent deep-sea sediments

NASA Astrophysics Data System (ADS)

Leinen, Margaret; Cwienk, Douglas; Heath, G. Ross; Biscaye, Pierre E.; Kolla, V.; Thiede, Jørn; Dauphin, J. Paul

1986-03-01

All available quartz and biogenic silica concentrations from deep-sea surface sediments were intercalibrated, plotted, and contoured on a calcium-carbonate-free basis. The maps show highest concentrations of biogenic silica (opal) along the west African coast, along equatorial divergences in all oceans, and at the Polar Front in the southern Indian Ocean. These are all areas where upwelling is strong and there is high biological productivity. Quartz in pelagic sediments deposited far from land is generally eolian in origin. Its distribution reflects dominant wind systems in the Pacific, but in much of the Atlantic and Indian oceans the distribution pattern is strongly modified by turbidite deposition and bottom current processes.

FIRE_ACE_C130_RAMS

Atmospheric Science Data Center

2017-04-26

... NCAR C-130 Instrument:  Radiation Measurement System Spatial Coverage:  Fairbanks, Alaska and the ... Parameters:  Upwelling and Downwelling Total Solar Flux Infrared Flux and Narrowband Flux Order Data:  ...

The phenomenon of bloom development of the invasive potentially toxic dinoflagellate Gonyaulax polygramma in deep water areas of the Caspian Sea

NASA Astrophysics Data System (ADS)

Pautova, L. A.; Kravchishina, M. D.; Silkin, V. A.; Lisitzin, A. P.

2017-06-01

This work presents the first data on the occurrence of the invasive, potentially toxic dinoflagellate Gonyaulax polygramma in the composition of plankton phytocenoses in the Caspian Sea. It was revealed that G. polygramma plays the key role in the quantitative characteristics of summer plankton phytocenoses and its bloom during the summer seasons of 2010 and 2013 was comparable in biomass (15-16 g/m3) to a "red tide." In addition, the correlation between the G. polygramma bloom and the wind upwelling system in the eastern mid-Caspian region was established. For the first time, it is suggested that "bloom" of G. polygramma can also occur in deep-water halistatic areas (Derbent depression), remote from the upwelling system.

Changes in the partial pressure of carbon dioxide in the Mauritanian-Cap Vert upwelling region between 2005 and 2012

NASA Astrophysics Data System (ADS)

González-Dávila, Melchor; Magdalena Santana Casiano, J.; Machín, Francisco

2017-08-01

Coastal upwellings along the eastern margins of major ocean basins represent regions of large ecological and economic importance due to the high biological productivity. The role of these regions for the global carbon cycle makes them essential in addressing climate change. The physical forcing of upwelling processes that favor production in these areas are already being affected by global warming, which will modify the intensity of upwelling and, consequently, the carbon dioxide cycle. Here, we present monthly high-resolution surface experimental data for temperature and partial pressure of carbon dioxide in one of the four most important upwelling regions of the planet, the Mauritanian-Cap Vert upwelling region, from 2005 to 2012. This data set provides direct evidence of seasonal and interannual changes in the physical and biochemical processes. Specifically, we show an upwelling intensification and an increase of 0.6 Tg yr-1 in CO2 outgassing due to increased wind speed, despite increased primary productivity. This increase in CO2 outgassing together with the observed decrease in sea surface temperature at the location of the Mauritanian Cap Blanc, 21° N, produced a pH rate decrease of -0.003 ± 0.001 yr-1.

Upwelling Scales off the Coast of Peru: Comparison of Observation and Model

NASA Astrophysics Data System (ADS)

Vazquez, J.; Chin, T. M.; Armstrong, E. M.

2014-12-01

Upwelling regions of the world's oceans are home to some of the most productive fisheries. Yet these coastal areas provide unique challenges for remote sensing from satellite platforms because of both their proximity to land (radar interference) and typically small horizontal scales (< 50km) of upwelling processes. Comparisons are performed on the gradient of sea surface temperature (SST) fields derived from multiple sources: 1) the 0.25 degree resolution National Climatic Data Center (NCDC) Optimally Interpolated AVHRR+in-situ or AVHRR_OI, data set. 2) the 1km resolution Multi-scale Ultra-high Resolution (MUR) gridded SST data set, 3) the 0.25 degree resolution SST derived from the WindSat microwave sensor, 4) a 2km version of the Estimating the Circulation and Climate of the Ocean Model (HECCO2). Temporal and spatial correlations between HECCO2 and MUR, as well as between HECCO2 and NCDC, are examined through the dominant singular vectors (eigenmodes) of the covariance matrix for each pair of data sets. In both cases the first mode of covariability accounts for over 90% of the total variance. A simple technique based on SST gradients is then applied to the first mode to determine the upwelling scales based on HECCO2, MUR, and NCDC. Longitudinal sections at 8S, 20S, and 30S indicate that the upwelling scale decreases between 8S and 20S. At 20S the first mode of covariability between MUR and HECCO2 indicate an upwelling scale between 25 and 50km. Results are consistent when compared with chlorophyll-a data from MODIS-Aqua. Such upwelling scales are not seen in the WindSat data and reduced in the NCDC data. A reduction of the upwelling scale by a factor 0.2 between 8S and 20S is consistent with a dependence on the Coriolis parameter. A major conclusion of the work is that magnitudes of SST gradient and upwelling scales derived from MUR are consistent with those of the HECCO2 for the test period of October-November 2011. Additionally, it is shown that to resolve upwelling scales near the coast high resolution infrared data must be used in the analysis. Microwave derived SSTs, such as those from WindSat are of limited value when upwelling scales are less then 50km.

Water masses in the Monterey Bay during the summer of 2000

NASA Astrophysics Data System (ADS)

Warn-Varnas, Alex; Gangopadhyay, Avijit; Hawkins, J. A.

2007-06-01

Water masses in Monterey Bay are determined from the CTD casts of the Monterey Ocean Observing System (MOOS) Upper-water-column Science Experiment (MUSE) August 2000 dataset. It is shown through cluster analysis that the MUSE 2000 CTD dataset contains 5 water masses. These five water masses are: bay surface water (BSW), bay warm water (BWW), bay intermediate water (BIW), sub arctic upper water (SUW) and North Pacific deep water (NPDW). The BWW is a new water mass that exists in one area and is attributed to the effects of solar heating. The volumes occupied by each of the water masses are obtained. The BIW water is the most dominant water mass and occupies 68.8% of the volume. The statistical means and standard deviations for each water parameter, including spiciness and oxygen concentration, are calculated during separate upwelling and relaxed periods. The water mass content and structure are analyzed and studied during upwelling and a relaxed period. During upwelling, along a CTD track off Pt. Ano Nuevo, the water mass T, S distribution tended to be organized along three branches. Off Pt. Ano Nuevo the innovative coastal observation network (ICON) model showed the formation of a cyclonic eddy during the analyzed upwelling period. In time the eddy moved southwest and became absorbed into the southerly flow during the initial phases of the following wind-relaxed period.

Radiolarian indicators of El Nino and anti-El Nino events in Holocene sediments of Santa Barbara basin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weinheimer, A.L.

Radiolarian distributions and physical oceanographic data from the Santa Barbara basin indicate the following. Strong anti-El Nino periods can be characterized by (1) intermediate radiolarian density, (2) high percentage of transition-central radiolarian fauna, and (3) low percentage and number of warm-water radiolarian fauna. This distribution pattern is attributed to strong wind-driven upwelling and reduced northward transport by the California Countercurrent during anti-El Nino periods. Strong El Nino periods are typically (1) high in radiolarian density, and (2) low in percentage but high in number of warm-water fauna. This distribution is attributed to reduced wind-driven upwelling, enhanced northward countercurrent transport, andmore » geostrophic doming of the cold-water masses in the shear zone between the California Current and California Countercurrent.« less

Phytoplankton Community Structure in 2011-2013 Compared to the Extratropical Warming Event of 2014-2015

NASA Astrophysics Data System (ADS)

Du, X.; Peterson, W. T.

2018-02-01

Coastal waters of the Northern California Current experienced "normal" ocean conditions in 2011-2012, weak upwelling in 2013-2014, then suddenly warmed in September 2014. The response of phytoplankton community structure to contrasting ocean conditions was determined from samples collected off Newport, Oregon. Cluster analysis identified three prominent phytoplankton community types: one that occurred during the upwelling season characterized by the highest abundance and diversity of diatoms, a preupwelling/relaxation community characterized by lower abundance, lowest diversity of diatoms and dinoflagellates, and another one associated with the warm anomalies from September 2014 through 2015 with reduced diatom abundance and diversity but the highest dinoflagellate diversity. The changes of diatom and dinoflagellate community were correlated with local factors (silicate, silicate: nitrate ratios, temperature, and salinity), and with the Pacific Decadal Oscillation.

Record of Cyclical Massive Upwellings from the Pacific Large Low Shear Velocity Province in the Mesozoic

NASA Astrophysics Data System (ADS)

Gazel, E.; Madrigal, P.; Flores, K. E.; Bizimis, M.; Jicha, B. R.

2016-12-01

Global tomography and numerical models suggest that mantle plume occurrences are closely linked to the margins of the large low shear velocity provinces (LLSVPs). In these locations the ascent of material from the core-mantle boundary connects the deep Earth with surface processes through mantle plume activity, forming large igneous provinces (LIPs) and some of the modern hotspot volcanoes. Petrological and geodynamic evidence suggest a link between the formation of oceanic plateaus and the interactions of mantle plumes and mid-ocean ridges (MOR). Therefore, it is possible to trace the potential interactions between MORs and deep mantle plume upwellings by referencing the tectonic and magmatic evolution of the Pacific Plate in time to the current location of the LLSVP, considering the long-lived ( 500 Ma) existence of these thermochemical anomalies. We identified episodic upwellings of the Pacific LLSVP during the Mesozoic separated by 10 to 20 Ma, by reconstructing the kinematic evolution of the Pacific Plate in the last 170 Ma. The fact that the bulk emplacement of LIPs ( 120-80 Ma) in the Pacific coincides with the timing of the Cretaceous Normal Superchron, that can be related to fluctuations of mantle-core heat fluxes further supports the hypothesis of deep mantle origin for LIPs. The potential cyclicity of LIP emplacement could be tied to core heat fluctuations interacting with the lower mantle, the rheology contrast of material crossing the transition zone (either upwelling hot material or downgoing dense slabs as mantle avalanches), the rate of entrainment of recycled materials, or a combination of the processes mentioned. Recognizing patterns and possible cycles is crucial to the link between deep processes and life as these pulses impacted the marine biota resulting in episodes of anoxia and mass extinctions shortly after their eruption.

Sensitivity of the Southern Ocean overturning circulation to surface buoyancy forcing

NASA Astrophysics Data System (ADS)

Morrison, A.; Hogg, A.; Ward, M.

2011-12-01

The southern limb of the ocean's meridional overturning circulation plays a key role in the Earth's response to climate change. The rise in atmospheric CO2 during glacial-interglacial transitions has been attributed to outgassing of enhanced upwelling water masses in the Southern Ocean. However a dynamical understanding of the physical mechanisms driving the change in overturning is lacking. Previous modelling studies of the Southern Ocean have focused on the effect of wind stress forcing on the overturning, while largely neglecting the response of the upper overturning cell to changes in surface buoyancy forcing. Using a series of eddy-permitting, idealised simulations of the Southern Ocean, we show that surface buoyancy forcing in the mid-latitudes is likely to play a significant role in setting the strength of the overturning circulation. Air-sea fluxes of heat and precipitation over the Antarctic Circumpolar Current region act to convert dense upwelled water masses into lighter waters at the surface. Additional fluxes of heat or freshwater thereby facilitate the meridional overturning up to a theoretical limit derived from Ekman transport. The sensitivity of the overturning to surface buoyancy forcing is strongly dependent on the relative locations of the wind stress profile, buoyancy forcing and upwelling region. The idealised model results provide support for the hypothesis that changes in upwelling during deglaciations may have been driven by changes in heat and freshwater fluxes, instead of, or in addition to, changes in wind stress. Morrison, A. K., A. M. Hogg, and M. L. Ward (2011), Sensitivity of the Southern Ocean overturning circulation to surface buoyancy forcing, Geophys. Res. Lett., 38, L14602, doi:10.1029/2011GL048031.

Longitudinal Biases in the Seychelles Dome Simulated by 34 Ocean-Atmosphere Coupled General Circulation Models

NASA Astrophysics Data System (ADS)

Nagura, M.; Sasaki, W.; Tozuka, T.; Luo, J.; Behera, S. K.; Yamagata, T.

2012-12-01

The upwelling dome of the southern tropical Indian Ocean is examined by using simulated results from 34 ocean-atmosphere coupled general circulation models (CGCMs) including those from the phase five of the Coupled Model Intercomparison Project (CMIP5). Among the current set of the 34 CGCMs, 12 models erroneously produce the upwelling dome in the eastern half of the basin while the observed Seychelles Dome is located in the southwestern tropical Indian Ocean (Figure 1). The annual mean Ekman pumping velocity is almost zero in the southern off-equatorial region in these models. This is in contrast with the observations that show Ekman upwelling as the cause of the Seychelles Dome. In the models that produce the dome in the eastern basin, the easterly biases are prominent along the equator in boreal summer and fall that cause shallow thermocline biases along the Java and Sumatra coasts via Kelvin wave dynamics and result in a spurious upwelling dome there. In addition, these models tend to overestimate (underestimate) the magnitude of annual (semiannual) cycle of thermocline depth variability in the dome region, which is another consequence of the easterly wind biases in boreal summer-fall. Compared to the CMIP3 models (Yokoi et al. 2009), the CMIP5 models are even worse in simulating the dome longitudes and magnitudes of annual and semiannual cycles of thermocline depth variability in the dome region. Considering the increasing need to understand regional impacts of climate modes, these results may give serious caveats to interpretation of model results and help in further model developments.; Figure 1: The longitudes of the shallowest annual-mean D20 in 5°S-12°S. The open and filled circles are for the observations and the CGCMs, respectively.

Climate variability and Dinophysis acuta blooms in an upwelling system.

PubMed

Díaz, Patricio A; Ruiz-Villarreal, Manuel; Pazos, Yolanda; Moita, Teresa; Reguera, Beatriz

2016-03-01

Dinophysis acuta is a frequent seasonal lipophilic toxin producer in European Atlantic coastal waters associated with thermal stratification. In the Galician Rías, populations of D. acuta with their epicentre located off Aveiro (northern Portugal), typically co-occur with and follow those of Dinophysis acuminata during the upwelling transition (early autumn) as a result of longshore transport. During hotter than average summers, D. acuta blooms also occur in August in the Rías, when they replace D. acuminata. Here we examined a 30-year (1985-2014) time series of D. acuta from samples collected by the same method in the Galician Rías. Our main objective was to identify patterns of distribution and their relation with climate variability, and to explain the exceptional summer blooms of D. acuta in 1989-1990. A dome-shaped relationship was found between summer upwelling intensity and D. acuta blooms; cell maxima were associated with conditions where the balance between upwelling intensity and heating, leading to deepened thermoclines, combined with tidal phase (3 days after neap tides) created windows of opportunity for this species. The application of a generalized additive model based on biological (D. acuta inoculum) and environmental predictors (Cumulative June-August upwelling CUI JJA , average June-August SST JJA and tidal range) explained more than 70% of the deviance for the exceptional summer blooms of D. acuta, through a combination of moderate (35,000-50,000m 3 s -1 km -1 ) summer upwelling (CUI JJA ), thermal stratification (SST JJA >17°C) and moderate tidal range (∼2.5m), provided D. acuta cells (inoculum) were present in July. There was no evidence of increasing trends in D. acuta bloom frequency/intensity nor a clear relationship with NAO or other long-term climatic cycles. Instead, the exceptional summer blooms of 1989-1990 appeared linked to extreme hydroclimatic anomalies (high positive anomalies in SST and NAO index), which affected most of the European Atlantic coast. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

Factors Impacting the Migration Paths of Humpback Whales, Megaptera novaeangliae, in Queensland, Australia

NASA Astrophysics Data System (ADS)

Lemckert, C. J.; Reinke, J.; Meynecke, O.

2016-02-01

Humpback whales, Megaptera novaeangliae, migrate annually from polar feeding grounds in summer to tropical breeding grounds in winter. Large scale migration patterns are quite well known; however, small scale distribution patterns and relationships with environmental conditions have received less attention. Protection from a range of threats, as well as predicting the effects of climate change, requires knowledge of preferred habitat and the reasons behind the preferences. East Australian humpback whales travel from the Southern Ocean, along the East Coast of Australia, to the Great Barrier Reef (or further) to breed. The East Australian coastal environment is dominated by the East Australian Current. This current carries warm water poleward from the tropics and is responsible for generating upwelling conditions on the coast and providing the majority of nutrients available for primary production. Sharp temperature changes develop at the border of the warm current and the cooler coastal and upwelled waters. This study investigates relationships between humpback whale distribution and environmental conditions (including bathymetry and remotely sensed sea surface temperature, as well as their gradients) on the Gold Coast and Hervey Bay, Australia. The Gold Coast is used primarily a migration route, but also provides a rest stop for mothers and calves on the return journey. Hervey Bay is used on the southern (return) migration for resting and socialising. Environmental preferences for these two will provide a comparison of the requirements for different habitat types. Initial outcomes of the study on the Gold Coast suggest a preference for cooler waters and in areas with a strong temperature gradient. The higher productivity in cooler upwelled water and fronts may provide the whales with a chance of opportunistic feeding, a rare occurrence on their prolonged journey. Following particular hydrodynamic features such as these, which generally run parallel to the shore, may also serve as a tool for navigation.

Does upwelling intensity influence feeding habits and trophic position of planktivorous fish?

NASA Astrophysics Data System (ADS)

Lopez-Lopez, Lucia; Preciado, Izaskun; Muñoz, Isabel; Decima, Moira; Molinero, Juan Carlos; Tel, Elena

2017-04-01

Food web configuration is shaped by many factors, including primary production patterns and oceanographic features, such as upwelling events. In this study, we investigate variability in the trophic position, food web interlinks and energy pathways of four planktivorous demersal fish in the Southern Bay of Biscay- NE Atlantic. The study area is exposed to upwelling events of varying intensity and shows a significant spatial gradient along the coast. The two sampling years were characterized by markedly different conditions, with weak summer upwelling in 2012 and an intense upwelling season in 2013. We used a complementary approach based on stomach content analysis (SCA) and stable isotope analysis (SIA) to test the effects of upwelling intensity and persistence on the food-web. In particular we investigated whether different intensities shift the main flow of energy between the pelagic and benthic energy pathways. We found conspicuous interannual changes in the isotopic POM, whose δ15N was 2.5‰ lower during the productive 2013 season. Interannual changes in the isotopic signature of the fish species were also detected, although their values did not mirror variability at the basal level. The SCA results did not match the isotopic changes, which likely reflected dietary adjustments of the species during summer. The upwelling intensity gradient along the coast did not affect the nitrogen isotopic ratio of any group, however there was a significant effect of such gradient on the carbon isotopic ratio of the fish and euphausiid species. This effect was likely related to the higher primary production associated with intense upwelling conditions.

Investigating the polar ionosphere during the development of neutral density enhancements on 24-25 September 2000

NASA Astrophysics Data System (ADS)

Horvath, Ildiko; Lovell, Brian C.

2017-04-01

We focus on the well-known northern daytime neutral density spikes detected by CHAMP on 25 September 2000 and related coupled magnetospheric-ionospheric-thermospheric processes. We investigate the underlying magnetic events and resultant thermospheric variations plus the state of the ionospheric polar region by employing multi-instrument CHAMP and DMSP data. Results show the unfolding of a weak (SYM-HMin ≈ -27 nT; 0345 UT) magnetic storm during which these northern density spikes occurred. Some smaller southern daytime density spikes were also detected prior to this storm on the previous day. All these density spikes were detected in or near polar convection flow channels (FCs). Each FC was characterized by strong antisunward zonal ion drifts that excited the zonal and meridional neutral winds leaving the signature of FC in the CHAMP neutral wind measurements and thus providing direct observational evidence of FC underlying the density spike. Additional to the small-scale field-aligned current (SS-FAC) filaments, the sudden intensifications of ionospheric closure current in the FC fueled the thermosphere and contributed to the development of upwelling and density spike. Some smaller density increases occurred due to the weak intensification of ionospheric closure currents. Equatorward (poleward) directed meridional neutral winds strengthened (weakened) the density spike by moving the neutral density up and along (down and against) the upwelling fueled by the ionospheric closure current and SS-FAC filaments.

Practical limitations on the use of diurnal temperature signals to quantify groundwater upwelling

USGS Publications Warehouse

Briggs, Martin A.; Lautz, Laura K.; Buckley, Sean F.; Lane, John W.

2014-01-01

Groundwater upwelling to streams creates unique habitat by influencing stream water quality and temperature; upwelling zones also serve as vectors for contamination when groundwater is degraded. Temperature time series data acquired along vertical profiles in the streambed have been applied to simple analytical models to determine rates of vertical fluid flux. These models are based on the downward propagation characteristics (amplitude attenuation and phase-lag) of the surface diurnal signal. Despite the popularity of these models, there are few published characterizations of moderate-to-strong upwelling. We attribute this limitation to the thermodynamics of upwelling, under which the downward conductive signal transport from the streambed interface occurs opposite the upward advective fluid flux. Governing equations describing the advection–diffusion of heat within the streambed predict that under upwelling conditions, signal amplitude attenuation will increase, but, counterintuitively, phase-lag will decrease. Therefore the extinction (measurable) depth of the diurnal signal is very shallow, but phase lag is also short, yielding low signal to noise ratio and poor model sensitivity. Conversely, amplitude attenuation over similar sensor spacing is strong, yielding greater potential model sensitivity. Here we present streambed thermal time series over a range of moderate to strong upwelling sites in the Quashnet River, Cape Cod, Massachusetts. The predicted inverse relationship between phase-lag and rate of upwelling was observed in the field data over a range of conditions, but the observed phase-lags were consistently shorter than predicted. Analytical solutions for fluid flux based on signal amplitude attenuation return results consistent with numerical models and physical seepage meters, but the phase-lag analytical model results are generally unreasonable. Through numerical modeling we explore reasons why phase-lag may have been over-predicted by the analytical models, and develop guiding relations of diurnal temperature signal extinction depth based on stream diurnal signal amplitude, upwelling magnitude, and streambed thermal properties that will be useful in designing future experiments.

Evaluation of the sinks and sources of atmospheric CO2 by artificial upwelling.

PubMed

Pan, Yiwen; Fan, Wei; Huang, Ting-Hsuan; Wang, Shu-Lun; Chen, Chen-Tung Arthur

2015-04-01

Artificial upwelling is considered a promising way to reduce the accumulation of anthropogenic carbon dioxide in the atmosphere. This practice could transport nutrient-rich deep water to the euphotic zone, enhance phytoplankton growth and consequently increase organic carbon exportation to the deep ocean via the biological pump. However, only a few studies quantitatively assess changes in oceanic CO2 uptake resulting from artificial upwelling. This article uses a simulation to examine the effect of hypothetical artificial upwelling-induced variations of CO2 fugacity in seawater (fCO2) using observed carbon and nutrient data from 14 stations, ranging from 21 to 43°N, in the West Philippine Sea (WPS), the East China Sea (ECS) and the Sea of Japan. Calculations are based on two basic assumptions: First, a near-field mixing of a nutrient-rich deep-ocean water plume in a stratified ocean environment is assumed to form given the presence of an artificial upwelling devise with appropriate technical parameters. Second, it is assumed that photosynthesis of marine phytoplankton could deplete all available nutrients following the stoichiometry of the modified Redfield ratio C/H/O/N/S/P=103.1/181.7/93.4/11.7/2.1/1. Results suggest artificial upwelling has significant effects on regional changes in sea-air differences (ΔfCO2sea-air) and the carbon sequestration potential (ΔfCO2mixed-amb). Large variations of ΔfCO2sea-air and ΔfCO2mixed-amb are shown to be associated with different regions, seasons and technical parameters of the artificial upwelling device. With proper design, it is possible to reverse the contribution of artificial upwelling from a strong CO2 source to sink. Thus, artificial upwelling has the potential to succeed as a geoengineering technique to sequester anthropogenic CO2, with appropriate technical parameters in the right region and season. Copyright © 2014 Elsevier B.V. All rights reserved.

Circulation, Water Temperature, and Larval Settlement Over the Inner Continental Shelves of the Santa Barbara Channel, California

NASA Astrophysics Data System (ADS)

Fewings, M. R.; Washburn, L.; Ohlmann, C.; Blanchette, C.; Caselle, J.; Gotschalk, C.

2008-12-01

We use seven-year time series of wind stress, water velocity, and temperature in 15-18 m water depth to describe the circulation and water temperature over the inner continental shelves of the Channel Islands and California mainland in the Santa Barbara Basin. This area is strongly influenced by the California Current upwelling system. In turn, the water circulation in the Santa Barbara Basin influences the local marine ecosystem by affecting the water temperature and the supply of nutrients and larval fish and invertebrates. Larvae and nutrients traveling from the coast to the open ocean and back again must somehow pass through the inner shelf. The water circulation over the inner continental shelf of the Northern Channel Islands has not been described. Due to the shallowness of the water, an inner shelf has different physical dynamics than either the surfzone or the middle and outer continental shelf. We discuss the relative importance of upwelling- favorable along-shelf winds and of cross-shelf winds as forcing mechanisms for coastal upwelling circulations over the inner shelf; test whether the cross-shelf wind stress and surface gravity waves are important for cross-shelf circulation in the Santa Barbara Basin; and describe the subtidal patterns of water temperature, stratification, and velocity around the Channel Islands and their relation to observed larval settlement patterns. Cross-shelf circulation and the movement of water masses into and out of the Basin have implications for settlement and recruitment of many coastal species, including the economically important kelp rockfish, kelp bass, and sea urchin. Understanding the circulation of the Santa Barbara Basin and its inner shelves is a precursor to determining the source locations of the planktonic larvae. That information on source locations is essential for the design, siting, and assessment of existing and future marine protected areas in California and elsewhere.

Sonar gas seepage characterization using high resolution systems at short ranges

NASA Astrophysics Data System (ADS)

Schneider von Deimling, J.; Lohrberg, A.; Mücke, I.

2017-12-01

Sonar is extremely sensitive in regard to submarine remote sensing of free gas bubbles. Known reasons for this are (1) high impedance contrast between water and gas, holding true also at larger depths with higher hydrostatic pressures and thus greater mole density in a gas bubble; (2) resonating behavior at a specific depth-frequency-size/shape relation with highly non-linear behavior; (3) an overlooked property being valuable for gas seepage detection and characterization is the movement of bubbles controlled by their overall trajectory governed by buoyancy, upwelling effects, tides, eddies, and currents. Moving objects are an unusual seismo-acoustic target in solid earth geophysics, and most processors hardly consider such short term movement. However, analyzing movement pattern over time and space highly improves human and algorithmic bubble detection and helps mitigation of false alarms often caused by fish's swim bladders. We optimized our sonar surveys for gas bubble trajectory analyses using calibrated split-beam and broadband/short pulse multibeam to gather very high quality sonar images. Thus we present sonar data patterns of gas seepage sites recorded at shorter ranges showing individual bubbles or groups of bubbles. Subsequent analyses of bubble trajectories and sonar strength can be used to quantify minor gas fluxes with high accuracy. Moreover, we analyzed strong gas bubble seepage sites with significant upwelling. Acoustic inversion of such major seep fluxes is extremely challenging if not even impossible given uncertainties in bubble size spectra, upwelling velocities, and beam geometry position of targets. Our 3D analyses of the water column multibeam data unraveled that some major bubble flows prescribe spiral vortex trajectories. The phenomenon was first found at an abandoned well site in the North Sea, but our recent investigations confirm such complex bubble trajectories exist at natural seeps, i.e. at the CO2 seep site Panarea (Italy). We hypothesize that accurate 3D analyses of plume shape and trajectory analyses might help to estimate threshold for fluxes.

Multiple dataset water-quality analyses in the vicinity of an ocean wastewater plume

NASA Technical Reports Server (NTRS)

Hamilton, Michael; Davis, Curtiss O.; Rhea, W. Joseph; Vandenbosch, Jeannette

1992-01-01

The White's Point ocean outfall is the method of disposal for approximately 374 million gallons of treated wastewater per day from Los Angeles County. The photosynthetic characteristics and particle distributions have well-defined properties that can be exploited to yield information on transport of the plume, mixing dynamics, and resuspension of bottom sediments during periods of bottom current velocity in excess of ca. 0.1 m/s. This plume of particles serves as a conservative tracer, which was studied using a number of sampling platforms and strategies, including underway sawtooth, or 'tow-yo' sampling, moored arrays of instruments, stationary profiling, and now for the first time with remotely-sensed multispectral color imagery. Research in this area previously focused on examination of the plume as it relates to the local current field and transport of particles, and on the resuspension of bottom sediments during periods of increased currents. In addition, Wu et al elucidated techniques for separating the particle signal into photosynthetic and nonphotosynthetic components, based on the beam attenuation to chlorophyll fluorescence ratio. High-frequency time series measurements of the current field and bio-optical characteristics at a site close to the waste diffusers were also collected. These are being analyzed for the spectral characteristics of the longer-timescale variability, in order to predict particle transport through simple meteorological measurements. With the advent of high spectral and spatial resolution imaging spectrometers such as AVIRIS, it is now possible to construct causal relationships between particle distributions and signature of the upwelled radiance from the surface. The availability of a constant and well-characterized source of material lends itself well to models which predict upwelled radiance from the surface. The availability of a constant and well-characterized source of material lends itself well to models which predict upwelled light as a function of particle distributions, photosynthetic pigments, colored dissolved organic material, and detrital and degradation products of photosynthesis. In addition, the spatial coverage provided by the tow-yo sampling device, combined with the profile measurements of the light field, should facilitate the best inverse modeling attempts possible thus far.

A Blueprint for the Ecological Monitoring of Australia's Oceans.

NASA Astrophysics Data System (ADS)

Bax, N. J.; Hayes, K. R.; Dambacher, J. M.; Hosack, G. R.; Dunstan, P. K.; Fulton, E.; Thompson, P. A.; Hartog, J. R.; Hobday, A. J.; Bradford, R.; Foster, S.; Hedge, P.; Smith, D.; Marshall, C. M.

2016-02-01

Monitoring Australia's marine area is fundamental to understanding and documenting how the ocean is changing in response to human pressures. Fifty-four key ecological features (KEFs) were identified as areas of particular value to the Australian Government over the last 8 years. These were divided into six reporting groups: areas of enhanced pelagic productivity, canyons, deep seabeds, seamounts, shelf reefs and seabeds. Ecosystem models were built for 33 KEF systems that have the strongest datasets, based on a theoretical understanding of how they function. Human pressures were identified by regional specialists and combined with the KEF models to create a set of medium-term pressure scenarios for each KEF. Between four and 25 pressure scenarios were identified for each KEF. Examples of human pressures include the strengthening of the East Australian Current and shifts in ocean upwelling due to climate change, major fluctuations in pelagic fish and fur seal populations, and fishing, shipping and oil and gas activities. KEF models encompass parts of the ecosystem that have potential to be monitored as long-term indicators that increase, decrease, or remain unchanged under each pressure scenario. Suitable indicators are those that respond in predictable ways across all pressure scenarios for a KEF. Results from pressure scenarios developed to test indicators for Australia's nine enhanced pelagic productivity KEFs will be presented. Satellite observations were analysed to tease out the long-term trend in phytoplankton and ocean upwelling. The comparison of predicted and observed trends in indicators leads to an improved understanding of KEF systems and the utility of the indicators. A change in indicator is a signal that something was happening to a valued system. The prediction-observation process would explain why. This process is repeatable and can be updated as new information comes available.

Nitrogen uptake of phytoplankton assemblages under contrasting upwelling and downwelling conditions: The Ría de Vigo, NW Iberia

NASA Astrophysics Data System (ADS)

Seeyave, Sophie; Probyn, Trevor; Álvarez-Salgado, Xosé Antón; Figueiras, Francisco G.; Purdie, Duncan A.; Barton, Eric D.; Lucas, Michael

2013-06-01

Regenerated production (including organic nitrogen) is shown here to be important in the Ría de Vigo (Galicia, NW Iberia) in supporting both harmful algal bloom communities during the downwelling season, but also (to a lesser extent) diatom communities during stratified periods of weak to moderate upwelling. The Galician Rías, situated in the Iberian upwelling system, are regularly affected by blooms of toxic dinoflagellates, which pose serious threats to the local mussel farming industry. These tend to occur towards the end of summer, during the transition from upwelling to downwelling favourable seasons, when cold bottom shelf waters in the rías are replaced by warm surface shelf waters. Nitrate, ammonium and urea uptake rates were measured in the Ría de Vigo during a downwelling event in September 2006 and during an upwelling event in June 2007. In September the ría was well mixed, with a downwelling front observed towards the middle of the ría and relatively high nutrient concentrations (1.0-2.6 μmol L-1 nitrate; 1.0-5.6 μmol L-1 ammonium; 0.1-0.8 μmol L-1 phosphate; 2.0-9.0 μmol L-1 silicic acid) were present throughout the water column. Ammonium represented more than 80% of the nitrogenous nutrients, and the phytoplankton assemblage was dominated by dinoflagellates and small flagellates. In June the water column was stratified, with nutrient-rich, upwelled water below the thermocline and warm, nutrient-depleted water in the surface. At this time, nitrate represented more than 80% of the nitrogenous nutrients, and a mixed diatom assemblage was present. Primary phytoplankton production during both events was mainly sustained by regenerated nitrogen, with ammonium uptake rates of 0.035-0.063 μmol N L-1 h-1 in September and 0.078-0.188 μmol N L-1 h-1 in June. Although f-ratios were generally low (<0.2) in both June and September, a maximum of 0.61 was reached in June due to higher nitrate uptake (0.225 μmol N L-1 h-1). Total nitrogen uptake was also higher during the upwelling event (0.153-0.366 in June and 0.053-0.096 μmol N L-1 h-1 in September). Nitrogen uptake kinetics demonstrated a strong preference for ammonium and urea over nitrate in June.

Submesoscale Structure of the California Current Near San Clemente Island

DTIC Science & Technology

1990-06-01

components at the 8 km line in figure 9 p• p - e 0 Fi u eOFS JSlIE DIS TAIIC I |MI .: ..- 1111 O, AIF | KA Figrellh. Vertical cross-section of standard...7. Huyer, Adriana and P. Michael Kosro, Mesoscale Surveys over the Shelf and Slope in the Upwelling Region Near Point Arena, California, J. Geophs

Sedimentation across the central California oxygen minimum zone: an alternative coastal upwelling sequence.

USGS Publications Warehouse

Vercoutere, T.L.; Mullins, H.T.; McDougall, K.; Thompson, J.B.

1987-01-01

Distribution, abundance, and diversity of terrigenous, authigenous, and biogenous material provide evidence of the effect of bottom currents and oxygen minimum zone (OMZ) on continental slope sedimentation offshore central California. Three major OMZ facies are identified, along the upper and lower edges of OMZ and one at its core.-from Authors

Aircraft Derived Low Level Winds and Upwelling Off the Peruvian Cost during March, April, and May 1977.

DTIC Science & Technology

1979-08-01

Force Institute of Technology (ATC) ~ vih -Patterson AFB,. OH 45433 19. KEY WORDS (Continue on reverse side if necessary and identify by block number) 20...per- manent high located west of Chile drives the consistent southerly winds, while the more variable ocean currents pro- vide the colder subsurface

A Numerical Study of the Effect of Periodic Nutrient Supply on Pathways of Carbon in a Coastal Upwelling Regime

NASA Technical Reports Server (NTRS)

Carr, Mary-Elena

1998-01-01

A size-based ecosystem model was modified to include periodic upwelling events and used to evaluate the effect of episodic nutrient supply on the standing stock, carbon uptake, and carbon flow into mesozooplankton grazing and sinking flux in a coastal upwelling regime. Two ecosystem configurations were compared: a single food chain made up of net phytoplankton and mesozooplankton (one autotroph and one heterotroph, A1H1), and three interconnected food chains plus bacteria (three autotrophs and four heterotrophs, A3H4). The carbon pathways in the A1H1 simulations were under stronger physical control than those of the A3H4 runs, where the small size classes are not affected by frequent upwelling events. In the more complex food web simulations, the microbial pathway determines the total carbon uptake and grazing rates, and regenerated nitrogen accounts for more than half of the total primary production for periods of 20 days or longer between events. By contrast, new production, export of carbon through sinking and mesozooplankton grazing are more important in the A1H1 simulations. In the A3H4 simulations, the turnover time scale of the autotroph biomass increases as the period between upwelling events increases, because of the larger contribution of slow-growing net phytoplankton. The upwelling period was characterized for three upwelling sites from the alongshore wind speed measured by the NASA Scatterometer (NSCAT) and the corresponding model output compared with literature data. This validation exercise for three upwelling sites and a downstream embayment suggests that standing stock, carbon uptake and size fractionation were best supported by the A3H4 simulations, while the simulated sinking fluxes are not distinguishable in the two configurations.

High frequency responses of nanoplankton and microplankton to wind-driven upwelling off northern Chile

NASA Astrophysics Data System (ADS)

Aguilera, Victor; Escribano, Ruben; Herrera, Liliana

2009-08-01

Autotrophic and heterotrophic nanoplankton and microplankton vary widely in quantity and composition in coastal upwelling zones, causing a highly heterogeneous distribution of food resources for higher trophic levels. Here, we assessed daily changes in size-fractioned biomass and community structure of nanoplankton and microplankton at two upwelling sites off northern Chile, Mejillones (23°S) and Chipana (21°S), during summer 2006, winter 2006 and summer 2007 as related to changes in oceanographic conditions upon upwelling variation. We found highly-significant changes in quantity and community structure (species diversity and richness) of both nanoplankton and microplankton fractions after 3-5 days of observations. These changes were coupled to an intermittent upwelling regime reflected in the alongshore component of the wind. After a few days the whole community was modified in terms of species and size structure. Over-imposing this variability, during winter 2006 there was a strong perturbation of remote origin that substantially impacted temperature, oxygenation and stratification of the water column. This "abnormal" warming event altered the upwelling regime, but its impact on abundance and composition of the nanoplankton and microplankton fractions was uncertain. Over the short-time scale however, we found a strong coupling between daily changes in the alongshore component of wind and nanoplankton and microplankton abundances and their structure. All these findings indicate that despite the high biological productivity of this upwelling region, high frequency variation induced by wind forcing may be a major regulator of food resources (quantity and quality) for primary consumers, such as zooplankton, fish larvae and benthic organisms in the near-shore area. This high frequency variation may also impose a key constrain for prey-predator encounter rates and survival of short-lived zooplankton and invertebrate and fish larvae in the upwelling zone.

40 CFR 451.21 - Effluent limitations attainable by the application of the best practicable control technology...

Code of Federal Regulations, 2012 CFR

2012-07-01

... Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS... as video cameras, digital scanning sonar, and upweller systems; monitoring of sediment quality...

40 CFR 451.21 - Effluent limitations attainable by the application of the best practicable control technology...

Code of Federal Regulations, 2014 CFR

2014-07-01

... Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS... as video cameras, digital scanning sonar, and upweller systems; monitoring of sediment quality...

40 CFR 451.21 - Effluent limitations attainable by the application of the best practicable control technology...

Code of Federal Regulations, 2013 CFR

2013-07-01

... Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS... as video cameras, digital scanning sonar, and upweller systems; monitoring of sediment quality...

A Biogeochemical Oceanographer at Sea: My Life with Nitrogen and a Nod to Silica

NASA Astrophysics Data System (ADS)

Dugdale, Richard C.

2018-01-01

My evolution from electrical engineering student to limnologist and then to oceanographer was a consequence of generous mentoring, which led to my use of the 15N tracer technique to measure nitrogen fixation in aquatic systems. The concept of new and regenerated production arose when I applied this method to measure nitrate and ammonium uptake in marine ecosystems. I then showed that enzyme kinetics could be applied to algal nitrogen uptake and used a silicate pump to explain silicate limitation of diatoms in coastal and equatorial upwelling systems. These concepts are now recognized as modern nutrient paradigms in biogeochemical oceanography. My interest in nutrients required field studies and led to my passion for the study of upwelling ecosystems and the establishment of two major international programs, with numerous advisors, collaborators, and students helping along the way.

Warming and Cooling: The Medieval Climate Anomaly in Africa and Arabia

NASA Astrophysics Data System (ADS)

Lüning, Sebastian; Gałka, Mariusz; Vahrenholt, Fritz

2017-11-01

The Medieval Climate Anomaly (MCA) is a well-recognized climate perturbation in many parts of the world, with a core period of 1000-1200 Common Era. Here we present a palaeotemperature synthesis for the MCA in Africa and Arabia, based on 44 published localities. The data sets have been thoroughly correlated and the MCA trends palaeoclimatologically mapped. The vast majority of available Afro-Arabian onshore sites suggest a warm MCA, with the exception of the southern Levant where the MCA appears to have been cold. MCA cooling has also been documented in many segments of the circum-Africa-Arabian upwelling systems, as a result of changes in the wind systems which were leading to an intensification of cold water upwelling. Offshore cores from outside upwelling systems mostly show warm MCA conditions. The most likely key drivers of the observed medieval climate change are solar forcing and ocean cycles. Conspicuous cold spikes during the earliest and latest MCA may help to discriminate between solar (Oort Minimum) and ocean cycle (Atlantic Multidecadal Oscillation, AMO) influence. Compared to its large share of nearly one quarter of the world's landmass, data from Africa and Arabia are significantly underrepresented in global temperature reconstructions of the past 2,000 years. Onshore data are still absent for most regions in Africa and Arabia, except for regional data clusters in Morocco, South Africa, the East African Rift, and the Levant coast. In order to reconstruct land palaeotemperatures more robustly over Africa and Arabia, a systematic research program is needed.

Total and mesoscale long-range offshore transport of organic carbon from the Canary Upwelling System to the open North Atlantic

NASA Astrophysics Data System (ADS)

Lovecchio, Elisa; Gruber, Nicolas; Münnich, Matthias; Byrne, David; Lachkar, Zouhair

2017-04-01

The ocean's biological pump is often simplified to a purely vertical process. Nevertheless, the horizontal transport of organic carbon can be substantial, especially in coastal regions such as the Canary Upwelling System (CanUS), one of the four major Eastern Boundary Upwelling Systems, characterized by high shelf productivity and an intense lateral exchange of mass and tracers with the adjacent oligotrophic waters. Despite its importance, the magnitude of this lateral flux has not yet been constrained. Here, we quantify the lateral export of organic carbon from the CanUS to the open North Atlantic using the Regional Ocean Modeling System (ROMS) coupled to a biogeochemical ecosystem module. The model is run on an Atlantic telescopic grid with a strong refinement towards the north-western African shelf, to combine an eddy-resolving resolution in the region of study with a full Atlantic basin perspective. Our results reveal that over the whole CanUS more than a third of the Net Community Production (NCP) in the nearshore 100 km is transported offshore, amounting to about 19 Tg C yr-1. The offshore transport dominates the lateral fluxes up to 1500 km into the subtropical North Atlantic, along the way adding organic carbon to the upper 100 m at rates of between 8% and 34% of the alongshore average NCP. The remineralization at depth of this extra organic carbon leads to strongly negative vertically-integrated NCP throughout the whole offshore region of the CanUS, i.e. it makes the offshore region net heterotrophic. Substantial subregional variability shapes the spatial pattern of the fluxes in the CanUS. In particular, the central subregion surrounding Cape Blanc is the most efficient in terms of collecting and laterally exporting the organic carbon, resulting in a sharp peak of watercolumn heterotrophy. A decomposition of the organic carbon fluxes into a time-mean component and a time-variable, i.e., mesoscale component reveals a large contribution of the mesoscale activity to the offshore flux of organic carbon at every latitude. The mesoscale offshore transport ranges in intensity between 20% and 50% of the mean flux, reaching as far offshore as the mean transport. In its alongshore component, the mesoscale transport opposes the mean transport, recirculating laterally the organic carbon against the mean currents. Fundamental differences between the contributions of filaments, cyclonic and anticyclonic eddies to the transport of organic carbon are highlighted and discussed in a subregional perspective.

Abyssal Upwelling and Downwelling and the role of boundary layers

NASA Astrophysics Data System (ADS)

McDougall, T. J.; Ferrari, R. M.

2016-02-01

The bottom-intensified mixing activity arising from the interaction of internal tides with bottom topography implies that the dianeutral advection in the ocean interior is downwards, rather than upwards as is required by continuity. The upwelling of Bottom Water through density surfaces in the deep ocean is however possible because of the sloping nature of the sea floor. A budget study of the abyss (deeper than 2000m) will be described that shows that while the upwelling of Bottom Water might be 25 Sv, this is achieved by very strong upwelling in the bottom turbulent boundary layer (of thickness 50m) of 100 Sv and strong downwelling in the ocean interior of 75 Sv. This downwelling occurs within 10 degrees of longitude of the continental boundaries. This near-boundary confined strong upwelling and downwelling clearly has implications for the Stommel-Arons circulation.

A two-way nested simulation of the oceanic circulation in the Southwestern Atlantic

NASA Astrophysics Data System (ADS)

Combes, Vincent; Matano, Ricardo P.

2014-02-01

This article presents the results of a high-resolution (1/12°), two-way nested simulation of the oceanic circulation in the southwestern Atlantic region. A comparison between the model results and extant observations indicates that the nested model has skill in reproducing the best-known aspects of the regional circulation, e.g., the volume transport of the ACC, the latitudinal position of the BMC, the shelf break upwelling of Patagonia, and the Zapiola Anticyclone. Sensitivity experiments indicate that the bottom stress parameterization significantly impacts the mean location of the Brazil/Malvinas Confluence and the transport of the Zapiola Anticyclone. The transport of the Brazil Current strengthens during the austral summer and weakens during the austral winter. These variations are driven by the wind stress curl over the southwestern Atlantic. The variations of the transport of the Malvinas Current are out of phase with those of the Brazil Current. Most of the seasonal variability of this current is concentrated in the offshore portion of the jet, the inshore portion has a weak seasonality that modulates the magnitude of the Patagonian shelf break upwelling. Using passive tracers we show that most of the entrainment of deep waters into the shelf occurs in the southernmost portion of the Patagonian shelf and along the inshore boundary of the Brazil Current. Shelf waters are preferentially detrained near the Brazil/Malvinas Confluence. Consistent with previous studies, our simulation also shows that south of ˜42°S the Malvinas Current is composed of two jets, which merge near 42°S to form a single jet farther north.

The Physical Oceanography of Australia's Sunshine Coast

NASA Astrophysics Data System (ADS)

Ribbe, Joachim

2017-04-01

Australia's Sunshine coast is located to the south of the Great Barrier Reef and Fraser Island between about 25 oS to 28 oS. With a width of nearly 70-80 km, the eastern Australian continental shelf is at its widest here. The shelf region is referred to as the Southeast Queensland Marine Coastal Zone due to its unique physical oceanographic characteristics. The most prominent large-scale oceanic feature is the southward flowing East Australian Current (EAC). It forms to the north of Fraser Island from Coral Sea outflows, intensifies, and follows the continental shelf as a swift continental shelf hugging current but variable in strength; stronger in the southern hemisphere summer and weaker in winter. Little attention has been paid to the physical oceanography of this region, although important physical processes take place that drive regional marine environmental conditions, drive cross-shelf exchanges and interactions with the EAC, and that represent marine connectivity processes significant to the larger scale eastern Australian fisheries. This presentation reviews recent discoveries that include the Southeast Fraser Island Upwelling System, the Fraser Island Gyre, and document the role of cyclonic mesoscale eddies in driving cross-shelf exchanges and contribute to the formation of the Fraser Island Gyre. The Southeast Fraser Island Upwelling System appears to be predominately driven by the interaction of the EAC with the continental shelf leading to the establishment of one of eight important marine ecological hotspots along the east Australian coast. The Fraser Island Gyre is most prominent during the southern hemisphere autumn and winter months. It is characterised by on-shelf northerly flow, turning eastward south of Fraser Island before joining the EAC. It emerges that cyclonic eddy formation as well as the south-easterly trade winds drive the gyre's establishment and strength. A census of short-lived (7-28 days) cyclonic eddies, the first for any western boundary current region, found that the Southeast Queensland Marine Coastal Zone appears to be characterised by the highest number of eddies found along the east Australian Coast. About 43% of all eddies or about 4-5 per year were detected and tracked in this region. All these recent discoveries were made possible by analysing data provided via Australia's Integrated Marine Observing System (IMOS). A future effort is to be made to obtain additional in-situ data in order to support these new findings.

Phytoplankton pigment patterns and wind forcing off central California

NASA Technical Reports Server (NTRS)

Abbott, Mark R.; Barksdale, Brett

1991-01-01

Mesoscale variability in phytoplankton pigment distributions of central California during the spring-summer upwelling season are studied via a 4-yr time series of high-resolution coastal zone color scanner imagery. Empirical orthogonal functions are used to decompose the time series of spatial images into its dominant modes of variability. The coupling between wind forcing of the upper ocean and phytoplankton distribution on mesoscales is investigated. Wind forcing, in particular the curl of the wind stress, was found to play an important role in the distribution of phytoplankton pigment in the California Current. The spring transition varies in timing and intensity from year to year but appears to be a recurrent feature associated with the rapid onset of the upwelling-favorable winds. Although the underlying dynamics may be dominated by processes other than forcing by wind stress curl, it appears that curl may force the variability of the filaments and hence the pigment patterns.

Ocean response to typhoons in the western North Pacific: Composite results from Argo data

NASA Astrophysics Data System (ADS)

Lin, Sheng; Zhang, Wen-Zhou; Shang, Shao-Ping; Hong, Hua-Sheng

2017-05-01

Composite structures of ocean temperature and salinity anomalies caused by tropical cyclones (TCs) or typhoons in the western North Pacific Ocean were obtained from Argo data. These structures were used to analyze ocean responses to typhoons and the dynamic mechanisms inherent in those responses with a particular focus on upwelling. TC-induced cooling is often strongly rightward-biased in the surface layer, and shifts toward the typhoon track at depths exceeding roughly 100 m. In the central water column within approximately 75 km of the typhoon track, subsurface warming predicted by vertical mixing is restrained and replaced by cooling due to upwelling. Upwelling contributes 15% on average to temperature cooling in the near surface layer (10-30 m), 84% in the subsurface layer (30-250 m) and 94% in the deep layer (250-600 m) during the period of 0.5-2.5 days after the typhoon's passage. It is suggested that the sea surface cooling effect of vertical mixing can be enhanced by the upwelling. The effect of upwelling is also prominent in the salinity response to typhoons. The composite results from the Argo data clearly reveal basic ocean responses to typhoons and indicate the important role of upwelling therein.

Ocean products delivered by the Mercator Ocean Service Department

NASA Astrophysics Data System (ADS)

Crosnier, L.; Durand, E.; Soulat, F.; Messal, F.; Buarque, S.; Toumazou, V.; Landes, V.; Drevillon, M.; Lellouche, J.

2008-12-01

The newly created Service Department at Mercator Ocean is now offering various services for academic and private ocean applications. Mercator Ocean runs operationally ocean forecast systems for the Global and North Atlantic Ocean. These systems are based on an ocean general circulation model NEMO as well as on data assimilation of sea level anomalies, sea surface temperature and temperature and salinity vertical profiles. Three dimensional ocean fields of temperature, salinity and currents are updated and available weekly, including analysis and 2 weeks forecast fields. The Mercator Ocean service department is now offering a wide range of ocean derived products. This presentation will display some of the various products delivered in the framework of academic and private ocean applications: " Monitoring of the ocean current at the surface and at depth in several geographical areas for offshore oil platform, for offshore satellite launch platform, for transatlantic sailing or rowing boat races. " Monitoring of ocean climate indicators (Coral bleaching...) for marine reserve survey; " Monitoring of upwelling systems for fisheries; " Monitoring of the ocean heat content for tropical cyclone monitoring. " Monitoring of the ocean temperature/salinity and currents to guide research vessels during scientific cruises. The Mercator Ocean products catalogue will grow wider in the coming years, especially in the framework of the European GMES MyOcean project (FP7).

Widespread kelp-derived carbon in pelagic and benthic nearshore fishes

USGS Publications Warehouse

von Biela, Vanessa R.; Newsome, Seth D.; Bodkin, James L.; Kruse, Gordon H.; Zimmerman, Christian E.

2016-01-01

Kelp forests provide habitat for diverse and abundant fish assemblages, but the extent to which kelp provides a source of energy to fish and other predators is unclear. To examine the use of kelp-derived energy by fishes we estimated the contribution of kelp- and phytoplankton-derived carbon using carbon (δ13C) and nitrogen (δ15N) isotopes measured in muscle tissue. Benthic-foraging kelp greenling (Hexagrammos decagrammus) and pelagic-foraging black rockfish (Sebastes melanops) were collected at eight sites spanning ∼35 to 60°N from the California Current (upwelling) to Alaska Coastal Current (downwelling) in the northeast Pacific Ocean. Muscle δ13C values were expected to be higher for fish tissue primarily derived from kelp, a benthic macroalgae, and lower for tissue primarily derived from phytoplankton, pelagic microalgae. Muscle δ13C values were higher in benthic-feeding kelp greenling than in pelagic-feeding black rockfish at seven of eight sites, indicating more kelp-derived carbon in greenling as expected. Estimates of kelp carbon contributions ranged from 36 to 89% in kelp greenling and 32 to 65% in black rockfish using carbon isotope mixing models. Isotopic evidence suggests that these two nearshore fishes routinely derive energy from kelp and phytoplankton, across coastal upwelling and downwelling systems. Thus, the foraging mode of nearshore predators has a small influence on their ultimate energy source as energy produced by benthic macroalgae and pelagic microalgae were incorporated in fish tissue regardless of feeding mode and suggest strong and widespread benthic-pelagic coupling. Widespread kelp contributions to benthic- and pelagic-feeding fishes suggests that kelp energy provides a benefit to nearshore fishes and highlights the potential for kelp and fish production to be linked.

Widespread kelp-derived carbon in pelagic and benthic nearshore fishes suggested by stable isotope analysis

NASA Astrophysics Data System (ADS)

von Biela, Vanessa R.; Newsome, Seth D.; Bodkin, James L.; Kruse, Gordon H.; Zimmerman, Christian E.

2016-11-01

Kelp forests provide habitat for diverse and abundant fish assemblages, but the extent to which kelp provides a source of energy to fish and other predators is unclear. To examine the use of kelp-derived energy by fishes we estimated the contribution of kelp- and phytoplankton-derived carbon using carbon (δ13C) and nitrogen (δ15N) isotopes measured in muscle tissue. Benthic-foraging kelp greenling (Hexagrammos decagrammus) and pelagic-foraging black rockfish (Sebastes melanops) were collected at eight sites spanning ∼35 to 60°N from the California Current (upwelling) to Alaska Coastal Current (downwelling) in the northeast Pacific Ocean. Muscle δ13C values were expected to be higher for fish tissue primarily derived from kelp, a benthic macroalgae, and lower for tissue primarily derived from phytoplankton, pelagic microalgae. Muscle δ13C values were higher in benthic-feeding kelp greenling than in pelagic-feeding black rockfish at seven of eight sites, indicating more kelp-derived carbon in greenling as expected. Estimates of kelp carbon contributions ranged from 36 to 89% in kelp greenling and 32 to 65% in black rockfish using carbon isotope mixing models. Isotopic evidence suggests that these two nearshore fishes routinely derive energy from kelp and phytoplankton, across coastal upwelling and downwelling systems. Thus, the foraging mode of nearshore predators has a small influence on their ultimate energy source as energy produced by benthic macroalgae and pelagic microalgae were incorporated in fish tissue regardless of feeding mode and suggest strong and widespread benthic-pelagic coupling. Widespread kelp contributions to benthic- and pelagic-feeding fishes suggests that kelp energy provides a benefit to nearshore fishes and highlights the potential for kelp and fish production to be linked.

Transmission of the haplosporidian parasite MSX Haplosporidium nelsoni to the eastern oyster Crassostrea virginica in an upweller system.

PubMed

Sunila, I; Karolus, J; Lang, E P; Mroczka, M E; Volk, J

2000-08-31

The haplosporidian oyster parasite MSX (Multinucleated Sphere X) Haplosporidium nelsoni was transmitted to eastern oysters Crassostrea virginica. Hatchery-raised, MSX-free juvenile oysters were placed in upweller tanks. Water to the tanks was filtered through a screen with 1 mm2 openings and originated from the water column overlaying naturally infected oysters beds (MSX prevalence 17 to 57%). MSX was diagnosed by histopathological analysis. MSX-disease (57% prevalence) with increased mortality (19%) was observed 11 wk after the beginning of the exposure and mortality of 80% after 16 wk. The study demonstrates transmission of MSX via water-borne infectious agents capable of passing through a 1 mm filter.

Kinematic and diabatic vertical velocity climatologies from a chemistry climate model

NASA Astrophysics Data System (ADS)

Marinke Hoppe, Charlotte; Ploeger, Felix; Konopka, Paul; Müller, Rolf

2016-05-01

The representation of vertical velocity in chemistry climate models is a key element for the representation of the large-scale Brewer-Dobson circulation in the stratosphere. Here, we diagnose and compare the kinematic and diabatic vertical velocities in the ECHAM/Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC) model. The calculation of kinematic vertical velocity is based on the continuity equation, whereas diabatic vertical velocity is computed using diabatic heating rates. Annual and monthly zonal mean climatologies of vertical velocity from a 10-year simulation are provided for both kinematic and diabatic vertical velocity representations. In general, both vertical velocity patterns show the main features of the stratospheric circulation, namely, upwelling at low latitudes and downwelling at high latitudes. The main difference in the vertical velocity pattern is a more uniform structure for diabatic and a noisier structure for kinematic vertical velocity. Diabatic vertical velocities show higher absolute values both in the upwelling branch in the inner tropics and in the downwelling regions in the polar vortices. Further, there is a latitudinal shift of the tropical upwelling branch in boreal summer between the two vertical velocity representations with the tropical upwelling region in the diabatic representation shifted southward compared to the kinematic case. Furthermore, we present mean age of air climatologies from two transport schemes in EMAC using these different vertical velocities and analyze the impact of residual circulation and mixing processes on the age of air. The age of air distributions show a hemispheric difference pattern in the stratosphere with younger air in the Southern Hemisphere and older air in the Northern Hemisphere using the transport scheme with diabatic vertical velocities. Further, the age of air climatology from the transport scheme using diabatic vertical velocities shows a younger mean age of air in the inner tropical upwelling branch and an older mean age in the extratropical tropopause region.

Re-Emergence of Excess Bomb Radiocarbon in Upwelling Waters with High-Latitude Origins

NASA Astrophysics Data System (ADS)

Lindsay, C. M.; Lehman, S.

2016-02-01

The quantity of radiocarbon (14C) in the atmosphere was nearly doubled by nuclear weapons testing in the 1960s. Since then, the terrestrial biosphere and the ocean have absorbed most of the excess 14C from the atmosphere, although atmospheric radiocarbon activity (∆14C) continues to decline due to ongoing emissions of 14C-free CO2 from combustion of fossil fuels. The large transient decline in atmospheric ∆14C combined with gas exchange at the surface and spatially variable time scales of ocean mixing have led to large ∆14C gradients in the surface ocean between upwelling- and downwelling-dominated regions. These gradients continue to evolve over time. We examine the rate of change of surface ocean ∆14C between CLIVAR (2000-2011) and WOCE era (1990s) or other slightly earlier (1980s) datasets and find spatial patterns that reveal mixing between 14C-enriched mode waters, 14C-depleted deep waters and surface waters that are well-equilibrated with the atmosphere. The ∆14C of mode water reaching equatorial upwelling regions has increased between the WOCE and CLIVAR time periods, and the greater contribution of 14C to the low-latitude surface ocean appears to have significantly offset the ∆14C decline otherwise imparted by air-sea gas exchange with the atmosphere. Consequently, ∆14C gradients between low-latitude upwelling regions and gyre centers have weakened proportionally more than between gyre centers and regions where pre-industrial water still upwells, such as the Southern Ocean. Properly accounting for the re-emergence of water with post-industrial characteristics is important to constrain earth system models that seek to explain DIC, pH and other anthropogenically perturbed tracers in the surface ocean. Because of the history of ∆14C in the atmosphere, ocean ∆14C is a useful tracer for this purpose.

Larval fish assemblages across an upwelling front: Indication for active and passive retention

NASA Astrophysics Data System (ADS)

Tiedemann, Maik; Brehmer, Patrice

2017-03-01

In upwelling areas, enrichment, concentration and retention are physical processes that have major consequences for larval fish survival. While these processes generally increase larval survival, strong upwelling can also increase mortality due to an offshore transport of larvae towards unfavorable habitats. In 2013 a survey was conducted along the Senegalese coast to investigate the upwelling effect with regard to larval fish assemblages and possible larval fish retention. According to water column characteristics two distinct habitats during an upwelling event were discriminated, i.e. the inshore upwelled water and the transition area over the deepest part of the Senegalese shelf. Along the two areas 42,162 fish larvae were collected representing 133 species within 40 families. Highest larval fish abundances were observed in the inshore area and decreasing abundances towards the transition, indicating that certain fish species make use of the retentive function of the inner shelf area as spawning grounds. Two larval fish assemblages overlap both habitats, which are sharply delimited by a strong upwelling front. One assemblage inhabited the inshore/upwelling area characterized by majorly neritic and pelagic species (Sparidae spp., Sardinella aurita), that seem to take the advantage of a passive retention on the shelf. The second assemblage consisted of a mix of pelagic and mesopelagic species (Engraulis encrasicolus, Carangidae spp. and Myctophidae spp.). Some species of the second assemblage, e.g. horse mackerels (Trachurus trachurus and Trachurus trecae), large finned-lantern fish (Hygophum macrochir) and foureyed sole (Microchirus ocellatus), revealed larval peak occurrences at intermediate and deep water layers, where the near-ground upwelling layer is able to transport larvae back to the shelf. This indicates active larval retention for species that are dominant in the transition area. Diel vertical migration patterns of S. aurita, E. encrasicolus and M. ocellatus revealed that a larval fish species may adapt its behavior to the local environment and do not necessarily follow a diurnal cycle. Field observations are essential to be integrated in larval drift models, since the vertical and horizontal larval distribution will have major consequences for survival. Comprehending larval survival mechanisms is necessary for the ultimate goal to understand and predict recruitment.

Export of Ice-Cavity Water from Pine Island Ice Shelf, West Antarctica

NASA Astrophysics Data System (ADS)

Thurnherr, Andreas; Jacobs, Stanley; Dutrieux, Pierre

2013-04-01

Stability of the West Antarctic Ice Sheet is sensitive to changes in melting at the bottom of floating ice shelves that form the seaward extensions of Antarctic glaciers flowing into the ocean. Not least because observations in the cavities beneath ice shelves are difficult, heat fluxes and melt rates have been inferred from oceanographic measurements obtained near the ice edge (calving fronts). Here, we report on a set of hydrographic and velocity data collected in early 2009 near the calving front of the Amundsen Sea's fast-moving and (until recently) accelerating Pine Island Glacier and its associated ice shelf. CTD profiles collected along the southern half of the meridionally-trending ice front show clear evidence for export of ice-cavity water. That water was carried in the upper ocean along the ice front by a southward current that is possibly related to a striking clockwise gyre that dominated the (summertime) upper-ocean circulation in Pine Island Bay. Signatures of ice-cavity water appear unrelated to current direction along most of the ice front, suggesting that cross-frontal exchange is dominated by temporal variability. However, repeated hydrographic and velocity measurements in a small "ice cove" at the southern end of the calving front show a persistent strong (mean velocity peaking near 0.5 ms-1) outflow of ice-cavity water in the upper 500 m. While surface features (boils) suggested upwelling from deep below the ice shelf, vertical velocity measurements reveal 1) that the mean upwelling within the confines of the cove was too weak to feed the observed outflow, and 2) that large high-frequency internal waves dominated the vertical motion of water inside the cove. These observations indicate that water exchange between the Pine Island Ice Shelf cavity and the Amundsen sea is strongly asymmetric with weak broad inflow at depth and concentrated surface-intensified outflow of melt-laden deep water at the southern edge of the calving front. The lack of significant mean upward motion within the cove strongly suggests that the upwelling takes place within the highly fractured ice along the southern shear margin of the ice shelf. If so, the upwelling water is likely to contribute to both the volume of apparent "basal" melting and to the weakness of that shear margin.

Typhoon Impacts

DTIC Science & Technology

2014-09-30

and Rmax is the radius of maximum winds . Figure 1 compares two properties of the cold wake, its location and its strength , from 6 storms. The...dimensional response of the underlying ocean including strong surface currents, upwelling of the thermocline, intense mixing across the thermocline, the...mixing determining the rate and character of wake dissipation. The wake is also expected to modify the atmospheric boundary layer and the biology

Emergence of burrowing urchins from California continental shelf sediments-A response to alongshore current reversals?

USGS Publications Warehouse

Nichols, F.H.; Cacchione, D.A.; Drake, D.E.; Thompson, J.K.

1989-01-01

Two sequences of bottom photographs taken every two or four hours for two months during the Coastal Ocean Dynamics Experiment (CODE) off the Russian River, California, reveal the dynamic nature of interations between the water column, the sediments, and benthic organisms in the mid-shelf silt deposit. Time-lapse photographs taken between late spring and early summer in 1981 and 1982 show that the subsurface-dwelling urchin Brisaster latifrons (one of the largest invertebrates found in shelf-depth fine sediment off the U.S. Pacific coast) occasionally emerged from the sediment, plowed the sediment surface during the course of a few hours to several days, then buried themselves again. Frame-by-frame study of the film sequences shows that the urchins typically emerged following relaxation of coastal upwelling, periods characterized by current direction reversals and increases in bottom water turbidity. Among the possible causes of the emergence of urchins and the consequent bioturbation of the upper few cm of sediment, a response to an enhanced food supply seems most plausible. Circumstantial evidence suggests the possibility that phytoplankton sedimentation during periods of upwelling relaxation could provide a new source of food at the sediment surface. ?? 1989.

Seasonal cooling and blooming in tropical oceans

NASA Astrophysics Data System (ADS)

Longhurst, Alan

1993-11-01

The relative importance of tropical pelagic algal blooms in not yet fully appreciated and the way they are induced not well understood. The tropical Atlantic supports pelagic blooms together equivalent to the North Atlantic spring bloom. These blooms are driven by thermocline tilting, curl of wind stress and eddy upwelling as the ocean responds to intensified basin-scale winds in boreal summer. The dimensions of the Pacific Ocean are such that seasonal thermocline tilting does not occur, and nutrient conditions are such that tilting might not induce bloom, in any case. Divergence at the equator is a separate process that strengthens the Atlantic bloom, is more prominent in the eastern Pacific, and in the Indian Ocean induces a bloom only in the western part of the ocean. Where western jet currents are retroflected from the coast off Somalia and Brazil, eddy upwelling induces prominent blooms. In the eastward flow of the northern equatorial countercurrents, positive wind curl stress induces Ekman pumping and the induction of algal blooms aligned with the currents. Some apparent algal bloom, such as that seen frequently in CZCS images westwards from Senegal, must be due to interference from airborne dust.

California State Waters Map Series: offshore of San Francisco, California

USGS Publications Warehouse

Cochrane, Guy R.; Johnson, Samuel Y.; Dartnell, Peter; Greene, H. Gary; Erdey, Mercedes D.; Golden, Nadine E.; Hartwell, Stephen R.; Endris, Charles A.; Manson, Michael W.; Sliter, Ray W.; Kvitek, Rikk G.; Watt, Janet Tilden; Ross, Stephanie L.; Bruns, Terry R.; Cochrane, Guy R.; Cochran, Susan A.

2015-01-01

Circulation over the continental shelf in the Offshore of San Francisco map area is dominated by the southward-flowing California Current, an eastern limb of the North Pacific Gyre that flows from Oregon to Baja California. At its midpoint offshore of central California, the California Current transports subarctic surface waters southeastward, about 150 to 1,300 km from shore. Seasonal northwesterly winds that are, in part, responsible for the California Current, generate coastal upwelling. Ocean temperatures offshore of central California have increased over the past 50 years, driving an ecosystem shift from the productive subarctic regime towards a depopulated subtropical environment.

Caanyon Mediated Cross-Slope Transport

NASA Astrophysics Data System (ADS)

Mihaly, S. F.; Cabrera De Leo, F.; Sastri, A. R.; Matabos, M.; Heesemann, M.; Ogata, B.

2017-12-01

Three current meter and water property stations along the west coast of Vancouver Island along with video and acoustic backscatter observations are used to gain insight into mechanisms of cross-slope transport. The setting is an eastern boundary current region with a active poleward flowing countercurrent. The significant effects of these currents flowing over a strongly incised continental slope along with cross-slope density flows are contrasted with the seasonally varying upwelling and downwelling regime. The video and acoustic backscatter enabled by Ocean Networks Canada's NEPTUNE observatory provide a view on the materials being transported between the abyssal plain and the continental shelf.

An Altimetry-Derived Index of the Offshore Forcing on the "Pressure Point" of the West Florida Shelf: Anomalous Upwelling and Its Influence on Harmful Algal Blooms

NASA Astrophysics Data System (ADS)

Liu, Y.; Weisberg, R. H.; Lenes, J. M.; Zheng, L.; Hubbard, K.; Walsh, J. J.

2017-12-01

Gulf of Mexico Loop Current (LC) interactions with the West Florida Shelf (WFS) slope play an important role in shelf ecology through the upwelling of new inorganic nutrients across the shelf break. This is particularly the case when the LC impinges upon the shelf slope in the southwest portion of the WFS near the Dry Tortugas. By contacting shallow water isobaths at this "pressure point" the LC forcing sets the entire shelf into motion. Characteristic patterns of LC interactions with the WFS and their occurrences are identified from altimetry data using unsupervised neural network, self-organizing map. The duration of the occurrences of such LC patterns is used as an indicator of offshore forcing of anomalous upwelling. Consistency is found between the altimetry-derived offshore forcing and the occurrence and severity of WFS coastal blooms of the toxic dinoflagellate, Karenia brevis: years without major blooms tend to have prolonged LC contact at the "pressure point," whereas years with major blooms tend not to have prolonged offshore forcing. Resetting the nutrient state of the shelf by the coastal ocean circulation in response to deep-ocean forcing demonstrates the importance of physical oceanography in shelf ecology. A satellite altimetry-derived seasonal predictor for major K. brevis blooms is also proposed.

Offshore forcing on the "pressure point" of the West Florida Shelf: Anomalous upwelling and its influence on harmful algal blooms

NASA Astrophysics Data System (ADS)

Liu, Yonggang; Weisberg, Robert H.; Lenes, Jason M.; Zheng, Lianyuan; Hubbard, Katherine; Walsh, John J.

2016-08-01

Gulf of Mexico Loop Current (LC) interactions with the West Florida Shelf (WFS) slope play an important role in shelf ecology through the upwelling of new inorganic nutrients across the shelf break. This is particularly the case when the LC impinges upon the shelf slope in the southwest portion of the WFS near the Dry Tortugas. By contacting shallow water isobaths at this "pressure point" the LC forcing sets the entire shelf into motion. Characteristic patterns of LC interactions with the WFS and their occurrences are identified using unsupervised neural network, self-organizing map, from 23 years (1993-2015) of altimetry data. The duration of the occurrences of such LC patterns is used as an indicator of offshore forcing of anomalous upwelling. Consistency is found between the altimetry-derived offshore forcing and the occurrence and severity of WFS coastal blooms of the toxic dinoflagellate, Karenia brevis: years without major blooms tend to have prolonged LC contact at the "pressure point," whereas years with major blooms tend not to have prolonged offshore forcing. Resetting the nutrient state of the shelf by the coastal ocean circulation in response to deep-ocean forcing demonstrates the importance of physical oceanography in shelf ecology. A satellite altimetry-derived seasonal predictor for major K. brevis blooms is also proposed.

Joint effect of freshwater plume and coastal upwelling on phytoplankton growth off the Changjiang River

NASA Astrophysics Data System (ADS)

Tseng, Y.-F.; Lin, J.; Dai, M.; Kao, S.-J.

2013-06-01

Changjiang River discharges vast amount of unbalanced nutrients (dissolved inorganic nitrogen (N) and phosphorus (P) with N / P > 80 in general) into the East China Sea during summertime. To explore nutrient dynamics and P stress potential for phytoplankton, a cruise was conducted in the Changjiang plume during summer 2011. With 3-D observations of nutrients, chlorophyll a (Chl a), and bulk alkaline phosphatase activity (APA), we concluded that the Changjiang Diluted Water (CDW) and coastal upwelling significantly influenced the horizontal and vertical heterogeneities of phytoplankton P-deficiency in the plume. Allochthonous APA was detected at nutrient-enriched freshwater end. Excessive N (~10 to 112 µM) was obserevd throughout the entire plume surface. In the plume fringe where featured by stratification and excess N, diapycnal phosphate supply was blocked to stimulate APA for phytoplankton growth. We observed upwelling outcrops just attaching the turbidity front at seaward side, where Chl a peaked yet much less APA was detected. An external phosphate supply from subsurface, which stimulated phytoplankton growth but inhibited APA, was suggested and the supply was likely sourced from the Nearshore Kuroshio Branch Current. In such hydrographically complicated Changjiang plume, phosphate supply instead of its concentration was more important determining the expression of APA. Meanwhile, allochthounous APA may also alter the usefulness of APA as a P-stress indicator.

Joint effect of freshwater plume and coastal upwelling on phytoplankton growth off the Changjiang River

NASA Astrophysics Data System (ADS)

Tseng, Y.-F.; Lin, J.; Dai, M.; Kao, S.-J.

2014-01-01

The Changjiang (Yangtze) River discharges vast amount of unbalanced nutrients (dissolved inorganic nitrogen and phosphorus with N / P ratio > 80 in general) into the East China Sea in summer. To study nutrient dynamics and P-stress potential for phytoplankton, a cruise was conducted in the Changjiang plume during summer 2011. With 3-D observations of nutrients, chlorophyll a (Chl a), and bulk alkaline phosphatase activity (APA), we concluded that the Changjiang Diluted Water and coastal upwelling significantly influenced the horizontal and vertical heterogeneities of phytoplankton P deficiency in the Changjiang plume. Allochthonous APA was detected at nutrient-enriched freshwater end. Excessive N (~ 10 to 112 μM) was observed throughout the entire plume surface. In the plume fringe featuring stratification and excess N, diapycnal phosphate supply was blocked and phytoplankton APA was stimulated for growth. We observed an upwelling just attaching to the turbidity front at seaward side where Chl a peaked yet much less APA was detected. An external phosphate supply from subsurface, which promoted phytoplankton growth but inhibited APA, was suggested to be sourced from the Nearshore Kuroshio Branch Current. In the so hydrographically complicated Changjiang plume, phosphate supply instead of its concentration may be more important in determining the expression of APA. Meanwhile, allochthonous APA may also alter the usefulness of APA as a P-stress indicator.

Submesoscale CO2 variability across an upwelling front off Peru

NASA Astrophysics Data System (ADS)

Köhn, Eike E.; Thomsen, Sören; Arévalo-Martínez, Damian L.; Kanzow, Torsten

2017-12-01

As a major source for atmospheric CO2, the Peruvian upwelling region exhibits strong variability in surface fCO2 on short spatial and temporal scales. Understanding the physical processes driving the strong variability is of fundamental importance for constraining the effect of marine emissions from upwelling regions on the global CO2 budget. In this study, a frontal decay on length scales of 𝒪(10 km) was observed off the Peruvian coast following a pronounced decrease in down-frontal (equatorward) wind speed with a time lag of 9 h. Simultaneously, the sea-to-air flux of CO2 on the inshore (cold) side of the front dropped from up to 80 to 10 mmol m-2 day-1, while the offshore (warm) side of the front was constantly outgassing at a rate of 10-20 mmol m-2 day-1. Based on repeated ship transects the decay of the front was observed to occur in two phases. The first phase was characterized by a development of coherent surface temperature anomalies which gained in amplitude over 6-9 h. The second phase was characterized by a disappearance of the surface temperature front within 6 h. Submesoscale mixed-layer instabilities were present but seem too slow to completely remove the temperature gradient in this short time period. Dynamics such as a pressure-driven gravity current appear to be a likely mechanism behind the evolution of the front.

Metagenomic Analysis of Upwelling-Affected Brazilian Coastal Seawater Reveals Sequence Domains of Type I PKS and Modular NRPS

PubMed Central

Cuadrat, Rafael R. C.; Cury, Juliano C.; Dávila, Alberto M. R.

2015-01-01

Marine environments harbor a wide range of microorganisms from the three domains of life. These microorganisms have great potential to enable discovery of new enzymes and bioactive compounds for industrial use. However, only ~1% of microorganisms from the environment can currently be identified through cultured isolates, limiting the discovery of new compounds. To overcome this limitation, a metagenomics approach has been widely adopted for biodiversity studies on samples from marine environments. In this study, we screened metagenomes in order to estimate the potential for new natural compound synthesis mediated by diversity in the Polyketide Synthase (PKS) and Nonribosomal Peptide Synthetase (NRPS) genes. The samples were collected from the Praia dos Anjos (Angel’s Beach) surface water—Arraial do Cabo (Rio de Janeiro state, Brazil), an environment affected by upwelling. In order to evaluate the potential for screening natural products in Arraial do Cabo samples, we used KS (keto-synthase) and C (condensation) domains (from PKS and NRPS, respectively) to build Hidden Markov Models (HMM) models. From both samples, a total of 84 KS and 46 C novel domain sequences were obtained, showing the potential of this environment for the discovery of new genes of biotechnological interest. These domains were classified by phylogenetic analysis and this was the first study conducted to screen PKS and NRPS genes in an upwelling affected sample PMID:26633360

Phytoplankton production and taxon-specific growth rates in the Costa Rica Dome

PubMed Central

Selph, Karen E.; Landry, Michael R.; Taylor, Andrew G.; Gutiérrez-Rodríguez, Andrés; Stukel, Michael R.; Wokuluk, John; Pasulka, Alexis

2016-01-01

During summer 2010, we investigated phytoplankton production and growth rates at 19 stations in the eastern tropical Pacific, where winds and strong opposing currents generate the Costa Rica Dome (CRD), an open-ocean upwelling feature. Primary production (14C-incorporation) and group-specific growth and net growth rates (two-treatment seawater dilution method) were estimated from samples incubated in situ at eight depths. Our cruise coincided with a mild El Niño event, and only weak upwelling was observed in the CRD. Nevertheless, the highest phytoplankton abundances were found near the dome center. However, mixed-layer growth rates were lowest in the dome center (∼0.5–0.9 day−1), but higher on the edge of the dome (∼0.9–1.0 day−1) and in adjacent coastal waters (0.9–1.3 day−1). We found good agreement between independent methods to estimate growth rates. Mixed-layer growth rates of Prochlorococcus and Synechococcus were largely balanced by mortality, whereas eukaryotic phytoplankton showed positive net growth (∼0.5–0.6 day−1), that is, growth available to support larger (mesozooplankton) consumer biomass. These are the first group-specific phytoplankton rate estimates in this region, and they demonstrate that integrated primary production is high, exceeding 1 g C m−2 day−1 on average, even during a period of reduced upwelling. PMID:27275025

Phytoplankton production and taxon-specific growth rates in the Costa Rica Dome.

PubMed

Selph, Karen E; Landry, Michael R; Taylor, Andrew G; Gutiérrez-Rodríguez, Andrés; Stukel, Michael R; Wokuluk, John; Pasulka, Alexis

2016-03-01

During summer 2010, we investigated phytoplankton production and growth rates at 19 stations in the eastern tropical Pacific, where winds and strong opposing currents generate the Costa Rica Dome (CRD), an open-ocean upwelling feature. Primary production ( 14 C-incorporation) and group-specific growth and net growth rates (two-treatment seawater dilution method) were estimated from samples incubated in situ at eight depths. Our cruise coincided with a mild El Niño event, and only weak upwelling was observed in the CRD. Nevertheless, the highest phytoplankton abundances were found near the dome center. However, mixed-layer growth rates were lowest in the dome center (∼0.5-0.9 day -1 ), but higher on the edge of the dome (∼0.9-1.0 day -1 ) and in adjacent coastal waters (0.9-1.3 day -1 ). We found good agreement between independent methods to estimate growth rates. Mixed-layer growth rates of Prochlorococcus and Synechococcus were largely balanced by mortality, whereas eukaryotic phytoplankton showed positive net growth (∼0.5-0.6 day -1 ), that is, growth available to support larger (mesozooplankton) consumer biomass. These are the first group-specific phytoplankton rate estimates in this region, and they demonstrate that integrated primary production is high, exceeding 1 g C m -2 day -1 on average, even during a period of reduced upwelling.

Impacts of the 2015-2016 El Niño on the California Current System: Early assessment and comparison to past events

NASA Astrophysics Data System (ADS)

Jacox, Michael G.; Hazen, Elliott L.; Zaba, Katherine D.; Rudnick, Daniel L.; Edwards, Christopher A.; Moore, Andrew M.; Bograd, Steven J.

2016-07-01

The 2015-2016 El Niño is by some measures one of the strongest on record, comparable to the 1982-1983 and 1997-1998 events that triggered widespread ecosystem change in the northeast Pacific. Here we describe impacts of the 2015-2016 El Niño on the California Current System (CCS) and place them in historical context using a regional ocean model and underwater glider observations. Impacts on the physical state of the CCS are weaker than expected based on tropical sea surface temperature anomalies; temperature and density fields reflect persistence of multiyear anomalies more than El Niño. While we anticipate El Niño-related impacts on spring/summer 2016 productivity to be similarly weak, their combination with preexisting anomalous conditions likely means continued low phytoplankton biomass. This study highlights the need for regional metrics of El Niño's effects and demonstrates the potential to assess these effects before the upwelling season, when altered ecosystem functioning is most apparent.

Geographical gradients in selection can reveal genetic constraints for evolutionary responses to ocean acidification

PubMed Central

Gaitán-Espitia, Juan Diego; Marshall, Dustin; Dupont, Sam; Bacigalupe, Leonardo D.; Bodrossy, Levente; Hobday, Alistair J.

2017-01-01

Geographical gradients in selection can shape different genetic architectures in natural populations, reflecting potential genetic constraints for adaptive evolution under climate change. Investigation of natural pH/pCO2 variation in upwelling regions reveals different spatio-temporal patterns of natural selection, generating genetic and phenotypic clines in populations, and potentially leading to local adaptation, relevant to understanding effects of ocean acidification (OA). Strong directional selection, associated with intense and continuous upwellings, may have depleted genetic variation in populations within these upwelling regions, favouring increased tolerances to low pH but with an associated cost in other traits. In contrast, diversifying or weak directional selection in populations with seasonal upwellings or outside major upwelling regions may have resulted in higher genetic variances and the lack of genetic correlations among traits. Testing this hypothesis in geographical regions with similar environmental conditions to those predicted under climate change will build insights into how selection may act in the future and how populations may respond to stressors such as OA. PMID:28148831

Estimates of upwelling rates in the Arabian Sea and the equatorial Indian Ocean based on bomb radiocarbon.

PubMed

Bhushan, R; Dutta, K; Somayajulu, B L K

2008-10-01

Radiocarbon measurements were made in the water column of the Arabian Sea and the equatorial Indian Ocean during 1994, 1995 and 1997 to assess the temporal variations in bomb 14C distribution and its inventory in the region with respect to GEOSECS measurements made during 1977-1978. Four GEOSECS stations were reoccupied (three in the Arabian Sea and one in the equatorial Indian Ocean) during this study, with all of them showing increased penetration of bomb 14C along with decrease in its surface water activity. The upwelling rates derived by model simulation of bomb 14C depth profile using the calculated exchange rates ranged from 3 to 9 m a(-1). The western region of the Arabian Sea experiencing high wind-induced upwelling has higher estimated upwelling rates. However, lower upwelling rates obtained for the stations occupied during this study could be due to reduced 14C gradient compared to that during GEOSECS.

Upwelling changes along the Arabian coast in a warming scenario

NASA Astrophysics Data System (ADS)

Praveen, V.; Ravindran, A. M.; Valsala, V.; Sandeep, S.

2016-12-01

The oceanic impact of poleward shift in Monsoon Low-Level Jet (MLLJ) is examined using a regional ocean model (ROMS). Two sets of downscaling experiments were conducted using ROMS with boundary and initial conditions from six CMIP5 models. While outputs from the historical run (1981-2000) acts as forcing for the first, the second uses RCP8.5 (2080-2099). By comparing the outputs, it is found that Oman coast will experience an increase in upwelling in tune with MLLJ shift. Consistent with the changes in upwelling and zonal Ekman transport, temperature, salinity and productivity show significant changes near the Oman coast. The changes in MLLJ causes the coastal wind to angle against the Oman coast in such a fashion that the net upwelling increases in the next century and so does the marine productivity. This study contrasts the general view of weakening of upwelling along the Arabian coasts due to the weakening of monsoon winds. Above findings has major implications on the livelihood and economy of the region

Precession-paced thermocline water temperature changes in response to upwelling conditions off southern Sumatra over the past 300,000 years

NASA Astrophysics Data System (ADS)

Wang, Xingxing; Jian, Zhimin; Lückge, Andreas; Wang, Yue; Dang, Haowen; Mohtadi, Mahyar

2018-07-01

Modern variations of sea surface temperature (SST) and thermocline water temperature (TWT) off southern Sumatra are responding to local upwelling conditions which are controlled by the Australian-Indonesian winter monsoon. The relationships between SST, TWT and upwelling during the past glacial-interglacial cycles are less clearly understood. In this study, SST and TWT variabilities over the past 300 kyr are reconstructed by using foraminiferal Mg/Ca-paleothermometry in sediment core SO139-74 KL off southern Sumatra (6°32.6‧S, 103°50‧E; 1690 m water depth). Whereas SST shows a clear glacial-interglacial cycle, TWT displays a predominant cycle at the precession band. Generally, the TWT record varies with total organic carbon content, revealing that similar to today, TWT and upwelling intensity off southern Sumatra vary in concert during the past 300 kyr. The lack of glacial-interglacial variability in the TWT suggests a limited role of glacial boundary conditions, such as changing sea level and ice volume, on the upwelling intensity in this region. The vertical gradients of upper water δ18O and temperature at this site also reveal precessional cyclicity. Our model simulation of air-sea interaction further supports the low TWTs during periods of enhanced upwelling and precession minimum.

A coupled ice-ocean model of upwelling in the marginal ice zone

NASA Technical Reports Server (NTRS)

Roed, L. P.; Obrien, J. J.

1983-01-01

A dynamical coupled ice-ocean numerical model for the marginal ice zone (MIZ) is suggested and used to study upwelling dynamics in the MIZ. The nonlinear sea ice model has a variable ice concentration and includes internal ice stress. The model is forced by stresses on the air/ocean and air/ice surfaces. The main coupling between the ice and the ocean is in the form of an interfacial stress on the ice/ocean interface. The ocean model is a linear reduced gravity model. The wind stress exerted by the atmosphere on the ocean is proportional to the fraction of open water, while the interfacial stress ice/ocean is proportional to the concentration of ice. A new mechanism for ice edge upwelling is suggested based on a geostrophic equilibrium solution for the sea ice medium. The upwelling reported in previous models invoking a stationary ice cover is shown to be replaced by a weak downwelling due to the ice motion. Most of the upwelling dynamics can be understood by analysis of the divergence of the across ice edge upper ocean transport. On the basis of numerical model, an analytical model is suggested that reproduces most of the upwelling dynamics of the more complex numerical model.

Different Levels of Hypoxia Tolerance during Early Life History Stages of Key Fish Species from the Northern Benguela Upwelling Ecosystem Inferred from the Comparison of Eco-Physiological Traits

NASA Astrophysics Data System (ADS)

Geist, S. J.; Imam, R. M.; Kunzmann, A.; Ekau, W.

2016-02-01

Global change factors such as a pronounced Oxygen Minimum Zone and the shoaling of hypoxic waters are assumed to play a major role in controlling the recruitment of fish stocks in Upwelling Systems by affecting the planktonic early life history stages. Ecological and ecophysiological traits in the larval stages of five key fish species in the Northern Benguela Upwelling System (Sardine, Sardinops sagax; Anchovy, Engraulis encrasicolus; Cape horse mackerel, Trachurus capensis; Cape hake, Merluccius sp.; Pelagic goby, Sufflogobobius bibarbatus) were investigated during the GENUS (Geochemistry and Ecology of the Namibian Upwelling Ecosystem) research project . Analysis of vertical larval distributions in relation to the depth of hypoxic water layers showed gradual interspecific differences, suggesting lower hypoxia tolerance levels of the small pelagics Sardine and Anchovy. Cape horse mackerel juveniles and larvae exhibited very high tolerance levels to short-term hypoxia in respirometry stress experiments, close to the levels of the extremely hypoxia-tolerant Pelagic goby. In the latter two species, we also measured the highest activities of anaerobic enzymes (pyruvate kinase and lactate dehydrogenase) in early and late larval stages, compared to very low activities in Sardine larvae. A higher amount of anaerobic enzymatic activity is related to a higher capacity to break down metabolites that build up during phases of oxygen debt and thus help the larvae to quickly recover from hypoxia exposure. In consequence, a high hypoxia tolerance during their early life stages allows Cape horse mackerel and Pelagic goby to successfully reproduce in an environment characterized by frequent hypoxic events. The low hypoxia tolerance of Sardine larvae, eventually resulting in higher mortality rates, is likely to be an important factor to understand the poor reproductive success and continuing recruitment failures of this formerly dominant fish species of the NBUS during the last 40 years.

Characteristics of the cold-water belt formed off Soya Warm Current

NASA Astrophysics Data System (ADS)

Ishizu, Miho; Kitade, Yujiro; Matsuyama, Masaji

2008-12-01

We examined the data obtained by acoustic Doppler current profiler, conductivity-temperature-depth profiler, and expendable bathythermograph observations, which were collected in the summers of 2000, 2001, and 2002, to clarify the characteristics of the cold-water belt (CWB), i.e., lower-temperature water than the surrounding water extending from the southwest coast of Sakhalin along the offshore side of Soya Warm Current (SWC) and to confirm one of the formation mechanisms of the CWB as suggested by our previous study, i.e., the upwelling due to the convergence of bottom Ekman transport off the SWC region. The CWB was observed at about 30 km off the coast, having a thickness of 14 m and a minimum temperature of 12°C at the sea surface. The CWB does not have the specific water mass, but is constituted of three representative water types off the northeast coast of Hokkaido in summer, i.e., SWC water, Fresh Surface Okhotsk Sea Water, and Okhotsk Sea Intermediate Water. In a comparison of the horizontal distributions of current and temperature, the CWB region is found to be advected to the southeast at an average of 40 ± 29% of the maximum current velocity of the SWC. The pumping speed due to the convergence of the bottom Ekman transport is estimated as (1.5-3.0) × 10-4 m s-1. We examined the mixing ratio of the CWB, and the results implied that the water mass of the CWB is advected southeastward and mixes with a water mass upwelling in a different region off SWC.

Identifying krill eggs in the central California current using novel multiplex PCR primers: Applications and limitations

NASA Astrophysics Data System (ADS)

Carrion, C. N.; Slesinger, E.; Marinovic, B.

2016-02-01

Euphausiids, otherwise known as krill, are an important link between primary producers and higher trophic levels within the central California current upwelling system. Euphausia pacifica and Thysanoessa spinifera, two of the most common euphausiid species along the central California coast, are both broadcast spawners and have some overlap in habitat, e.g. near marine life hotspots like the Monterey Bay and Gulf of Farallones. Species composition of euphausiid egg population within these regions is currently unknown. Distinct morphological differences between their eggs are lost once the egg dies or is preserved via formalin, alcohol, or freezing. In this project we designed genus specific DNA primers (mtCOI) for use in a multiplex PCR to distinguish among spawned euphausiid eggs of Euphausia spp. and Thysanoessa spp. in central California current surface waters. Effective and ineffective application of primers in a multiplex versus single-plex PCR is discussed, with an emphasis on primer design limitations in reference to the available barcoded regions of mitochondrial cytochrome oxidase subunit I (mtCOI) for each species in GenBank. This new protocol expands current monitoring efforts into sampling a non-swimming portion of the population which has the potential to improve euphausiid biomass estimates.

Geochemical and statistical evidence of recharge, mixing, and controls on spring discharge in an eogenetic karst aquifer

NASA Astrophysics Data System (ADS)

Moore, Paul J.; Martin, Jonathan B.; Screaton, Elizabeth J.

2009-10-01

SummaryInformation about sources of recharge, distributions of flow paths, and the extent of water-rock reactions in karst aquifers commonly result from monitoring spring chemistry and discharge. To investigate the relationship between spring characteristics and the complexities of karst aquifers, we couple variations in surface- and groundwater chemistry to physical conditions including river stage, precipitation, and evapotranspiration (ET) within a sink-rise system through a 6-km portion of the Upper Floridan aquifer (UFA) in north-central Florida. Principal component analysis (PCA) of time series major-element compositions suggests that at least three sources of water affect spring discharge, including allogenic recharge into a swallet, diffuse recharge through a thin vadose zone, and water upwelling from deep within the aquifer. The deep-water source exerts the strongest influence on water chemistry by providing a majority of Na +, Mg 2+, K +, Cl -, and SO42- to the system. Anomalously high temperature at one of several monitoring wells reflects vertical flow of about 1 m/year. Mass-balance calculations suggest diffuse recharge and deep-water upwelling can provide up to 50% of the spring discharge; however, their contributions depend on head gradients between the conduit and surrounding aquifer matrix, which are influenced by variations in precipitation, ET, and river stage. Our results indicate that upwelling from deep flow paths may provide significant contributions of water to spring discharge, and that monitoring only springs limits interpretations of karst systems by masking critical components of the aquifer, such as water sources and flow paths. These results also suggest the matrix in eogenetic aquifers is a major pathway for flow even in a system dominated by conduits.

Regional Climate Modelling of the Western Iberian Low-Level Wind Jet

NASA Astrophysics Data System (ADS)

Soares, Pedro M. M.; Lima, Daniela C. A.; Cardoso, Rita M.; Semedo, Álvaro

2016-04-01

The Iberian coastal low-level jet (CLLJ) is one the less studied boundary layer wind jet features in the Eastern Boundary Currents Systems (EBCS). These regions are amongst the most productive ocean ecosystems, where the atmosphere-land-ocean feedbacks, which include marine boundary layer clouds, coastal jets, upwelling and inland soil temperature and moisture, play an important role in defining the regional climate along the sub-tropical mid-latitude western coastal areas. Recently, the present climate western Iberian CLLJ properties were extensively described using a high resolution regional climate hindcast simulation. A summer maximum frequency of occurrence above 30% was found, with mean maximum wind speeds around 15 ms-1, between 300 and 400m heights (at the jet core). Since the 1990s the climate change impact on the EBCS is being studied, nevertheless some lack of consensus still persists regarding the evolution of upwelling and other components of the climate system in these areas. However, recently some authors have shown that changes are to be expected concerning the timing, intensity and spatial homogeneity of coastal upwelling and of CLLJs, in response to future warming, especially at higher latitudes, namely in Iberia and Canaries. In this study, the first climate change assessment study regarding the Western Iberian CLLJ, using a high resolution (9km) regional climate simulation, is presented. The properties of this CLLJ are studied and compared using two 30 years simulations: one historical simulation for the 1971-2000 period, and another simulation for future climate, in agreement with the RCP8.5 scenario, for the 2071-2100 period. Robust and consistent changes are found: 1) the hourly frequency of occurrence of the CLLJ is expected to increase in summer along the western Iberian coast, from mean maximum values of around 35% to approximately 50%; 2) the relative increase of the CLLJ frequency of occurrence is higher in the north off western Iberia; 3) the occurrence of the CLLJ covers larger areas both latitudinal and longitudinal; 4) the CLLJ season is enlarged extending to May and September; and, 5) there are shifts for higher occurrences of higher wind speeds and for the jet core to occur at higher heights. Publication supported by project FCT UID/GEO/50019/2013 - Instituto Dom Luiz - University of Lisbon

Seasonal and Interannual Variability in Gulf of Maine Hydrodynamics: 2002-2011.

PubMed

Li, Yizhen; He, Ruoying; McGillicuddy, Dennis J

2014-05-01

In situ observations including long-term moored meteorological and oceanographic measurements and multi-year gulf-wide ship survey data are used to quantify interannual variability of surface wind, river runoff, and hydrographic conditions in the Gulf of Maine during summers 2002-2011. The cumulative upwelling index shows that upwelling (downwelling)-favorable wind conditions were most persistent in 2010 (2005) over the 10-year study period. River discharge was highest in 2005; peak runoff occurred in early April in 2010 as opposed to late April to middle May in other years. Moored time series show that coastal water temperature was 0.5-2 °C warmer than average in summer 2010, and about 2 °C colder than average in 2004. Coastal salinity in April 2010 was the lowest in the 10-year study period. Both moored Acoustic Doppler Current Profiler (ADCP) current measurements and dynamic height/geostrophic velocity calculations based on gulf-wide ship survey data show May-June 2010 had one of the weakest alongshore transports in the western Gulf of Maine during the 10-year study period, likely associated with intrusions of warm slope water and fresher-than-usual Scotian Shelf water. Comparisons of coastal currents to the Paralytic Shellfish Poisoning (PSP) closure maps resulting from A. fundyense blooms suggest a linkage between alongshore transport and the downstream extent of toxicity.

Developments in Coastal Ocean Modeling

NASA Astrophysics Data System (ADS)

Allen, J. S.

2001-12-01

Capabilities in modeling continental shelf flow fields have improved markedly in the last several years. Progress is being made toward the long term scientific goal of utilizing numerical circulation models to interpolate, or extrapolate, necessarily limited field measurements to provide additional full-field information describing the behavior of, and providing dynamical rationalizations for, complex observed coastal flow. The improvement in modeling capabilities has been due to several factors including an increase in computer power and, importantly, an increase in experience of modelers in formulating relevant numerical experiments and in analyzing model results. We demonstrate present modeling capabilities and limitations by discussion of results from recent studies of shelf circulation off Oregon and northern California (joint work with Newberger, Gan, Oke, Pullen, and Wijesekera). Strong interactions between wind-forced coastal currents and continental shelf topography characterize the flow regimes in these cases. Favorable comparisons of model and measured alongshore currents and other variables provide confidence in the model-produced fields. The dependence of the mesoscale circulation, including upwelling and downwelling fronts and flow instabilities, on the submodel used to parameterize the effects of small scale turbulence, is discussed. Analyses of model results to provide explanations for the observed, but previously unexplained, alongshore variability in the intensity of coastal upwelling, which typically results in colder surface water south of capes, and the observed development in some locations of northward currents near the coast in response to the relaxation of southward winds, are presented.

Variability of the western Galician upwelling system (NW Spain) during an intensively sampled annual cycle. An EOF analysis approach

NASA Astrophysics Data System (ADS)

Herrera, J. L.; Rosón, G.; Varela, R. A.; Piedracoba, S.

2008-07-01

The key features of the western Galician shelf hydrography and dynamics are analyzed on a solid statistical and experimental basis. The results allowed us to gather together information dispersed in previous oceanographic works of the region. Empirical orthogonal functions analysis and a canonical correlation analysis were applied to a high-resolution dataset collected from 47 surveys done on a weekly frequency from May 2001 to May 2002. The main results of these analyses are summarized bellow. Salinity, temperature and the meridional component of the residual current are correlated with the relevant local forcings (the meridional coastal wind component and the continental run-off) and with a remote forcing (the meridional temperature gradient at latitude 37°N). About 80% of the salinity and temperature total variability over the shelf, and 37% of the residual meridional current total variability are explained by two EOFs for each variable. Up to 22% of the temperature total variability and 14% of the residual meridional current total variability is devoted to the set up of cross-shore gradients of the thermohaline properties caused by the wind-induced Ekman transport. Up to 11% and 10%, respectively, is related to the variability of the meridional temperature gradient at the Western Iberian Winter Front. About 30% of the temperature total variability can be explained by the development and erosion of the seasonal thermocline and by the seasonal variability of the thermohaline properties of the central waters. This thermocline presented unexpected low salinity values due to the trapping during spring and summer of the high continental inputs from the River Miño recorded in 2001. The low salinity plumes can be traced on the Galician shelf during almost all the annual cycle; they tend to be extended throughout the entire water column under downwelling conditions and concentrate in the surface layer when upwelling favourable winds blow. Our evidences point to the meridional temperature gradient acting as an important controlling factor of the central waters thermohaline properties and in the development and decay of the Iberian Poleward Current.

Emergy analysis of coastal systems influenced by upwelling in northern Chile: Estimation of ecological-economic sustainability at multiple scales

EPA Science Inventory

Numerous studies carried out in a variety of environments have suggested that coastal marine systems generate a variety of goods and services for humanity. However, in recent decades there has been a marked degradation of these ecosystems, as well as over-exploitation of natural ...

Dynamics of plankton populations in upwelling areas. [by remote sensors

NASA Technical Reports Server (NTRS)

Szekielda, K.

1974-01-01

Recent investigations of the upwelling area along the NW Coast of Africa which include studies with satellites are discussed. The detection of patchiness in temperature and plankton distribution in the upwelling area is of special interest because they can be investigated from space synoptically with repeated coverage. The recent satellite missions provide recordings in the infrared region of the electromagnetic spectrum (EMR) as well as in the visible part. The information from those two parts of the EMR is useful for establishing the sea surface temperature and plankton distribution in upwelling areas. The temperature distribution as observed with infrared sensors and the patchiness in plankton patterns are discussed as observed with the most recent satellites, namely the Earth Resources Technology Satellite (ERTS) and NOAA-2.

Atoll-phosphate genesis: Role of lagoonal biomass and possible role of endo-upwelling processes in phosphate concentration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trichet, J.; Rougerie, F.

1990-06-01

Sedimentological and hydrogeological data in Niau, a closed atoll in French Polynesia where P-concentration has been measured, suggest the role played by lagoonal organic matter in P-accumulation and the possible role of endo-upwelling processes in P-input in the system. A 15 m deep core through the lagoonal deposits shows the succession of organic-rich strata in which the P-content can reach up to 1.3% P{sub 2}O{sub 5}. Such a pattern suggests that, whatever the source of P within the lagoon (lagoonal water, bird guano, or endo-upwelled solutions, see below), this element is likely to be incorporated in quantitatively important lagoonal biomassmore » whose decay releases phosphorus back to the sediment. An example of such biomass and organic matter is given by the large amounts of cyano-bacterial organic matter that are present in the lagoon of Niau. A source for island phosphate has recently been proposed to be relatively deep seawater, which would be endo-upwelled from depths of hundreds of meters ({approximately}500 m, where P content is approximately 1.5 mmol.m{sup {minus}3} PO{sub 4}-P) through the permeable reef-body up to its surface (i.e., to its lagoonal waters, where P content reaches 5 mmol.m{sup {minus}3} in Niau atoll). The energy necessary for the transport of such solutions would be geothermal (at the bottom of the water column, i.e., close to the volcanic substrate of the reef body) and solar at its top through evaporation.« less

Controls on the interannual variability of hypoxia in a subtropical embayment and its adjacent waters in the Guangdong coastal upwelling system, northern South China Sea

NASA Astrophysics Data System (ADS)

Zhang, Heng; Cheng, Weicong; Chen, Yuren; Yu, Liuqian; Gong, Wenping

2018-06-01

Coastal embayments located downwind of large rivers under an upwelling-favorable wind are prone to develop low-oxygen or hypoxic conditions in their bottom water. One such embayment is Mirs Bay, off the Guangdong coast, which is affected by upwelling and the Pearl River Estuary (PRE) plume during summer. The relative importance of physical and biochemical processes on the interannual variability of hypoxia in Mirs Bay and its adjacent waters was investigated using statistical analyses of monthly hydrographic and water quality monitoring data from 2001 to 2015. The results reveal that the southwesterly wind duration and the PRE river discharge together explain 49% of the interannual variability in the size of the hypoxic area, whereas inclusion of the nutrient concentrations inside Mirs Bay and phytoplankton on the shelf explains 75% of the interannual variability in the size of the hypoxic area. This finding suggests that the interannual variability of hypoxia in Mirs Bay is regulated by coupled physical and biochemical processes. Increase of the hypoxic area under a longer-lasting southwesterly wind is caused by increased stratification, extended bottom water residence time, and onshore transport of a low-oxygen water mass induced by stable upwelling. In contrast, a reduction in the size of the hypoxic area may be attributed to a decrease in the surface water residence time of the particulate organic matter outside Mirs Bay due to increased discharge from the PRE. The results also show that the effects of allochthonous particulate organic matter outside Mirs Bay on bottom hypoxia cannot be neglected.

Three-Dimensional Numerical Simulation on Passively Excited Flows by Distributed Local Hot Sources Settled at the D" Layer Below Hotspots and/or Large-Scale Cool Masses at Subduction Zones Within the Static Layered Mantle

NASA Astrophysics Data System (ADS)

Eguchi, T.; Matsubara, K.; Ishida, M.

2001-12-01

To unveil dynamic process associated with three-dimensional unsteady mantle convection, we carried out numerical simulation on passively exerted flows by simplified local hot sources just above the CMB and large-scale cool masses beneath smoothed subduction zones. During the study, we used our individual code developed with the finite difference method. The basic three equations are for the continuity, the motion with the Boussinesq (incompressible) approximation, and the (thermal) energy conservation. The viscosity of our model is sensitive to temperature. To get time integration with high precision, we used the Newton method. In detail, the size and thermal energy of the hot or cool sources are not uniform along the latitude, because we could not select uniform local volumes assigned for the sources within the finite difference grids throughout the mantle. Our results, thus, accompany some latitude dependence. First, we treated the case of the hotspots, neglecting the contribution of the subduction zones. The local hot sources below the currently active hotspots were settled as dynamic driving forces included in the initial condition. Before starting the calculation, we assumed that the mantle was statically layered with zero velocity component. The thermal anomalies inserted instantaneously in the initial condition do excite dynamically passive flows. The type of the initial hot sources was not 'plume' but 'thermal.' The simulation results represent that local upwelling flows which were directly excited over the initial heat sources reached the upper mantle by approximately 30 My during the calculation. Each of the direct upwellings above the hotspots has its own dynamic potential to exert concentric down- and up-welling flows, alternately, at large distances. Simultaneously, the direct upwellings interact mutually within the spherical mantle. As an interesting feature, we numerically observed secondary upwellings somewhere in a wide region covering east Eurasia to the Bering Sea where no hot sources were initially input. It seems that the detailed location of the secondary upwellings depends partly on the numerical parameters such as the radial profile of mantle viscosity especially at the D" layer, etc., because the secondary flows are provoked by dynamic interaction among the distributed direct upwellings just above the CMB. Our results suggest that if we assume not only non-zero time delays during the input of the local hot sources but also parameters related with the difference of their historical surface flux rates, the pattern of the passively excited flows will be different from that obtained with the simultaneously settled hot sources stated above. Second, we simultaneously incorporated simplified thermal anomaly models associated with both the distributed local hotspots and the global subduction zones, as dynamic origins in the initial condition for the static layered mantle. In this case, the simulation result represents that the pattern of secondary radial flows, being different from those in the earlier case, is sensitive to the relative strength between the positive dynamic buoyancy integrated over all of the local hot sources below the hotspots and the total negative buoyancy beneath the subduction zones.

Predicting Trophic Interactions and Habitat Utilization in the California Current Ecosystem

DTIC Science & Technology

2015-09-30

spatial and temporal distribution of key marine organisms over multiple trophic levels, and (2) natural and anthropogenic variability in ecosystem...areas of climate modeling in upwelling regions (E. Curchitser), physical-biological modeling in the CCLME (J. Fiechter and C. Edwards), data...optimal growth conditions). By comparing interannual changes in fat depot against EOF modes for environmental variability (i.e., SST) and prey

Do submesoscale frontal processes ventilate the oxygen minimum zone off Peru?

NASA Astrophysics Data System (ADS)

Thomsen, S.; Kanzow, T.; Colas, F.; Echevin, V.; Krahmann, G.; Engel, A.

2016-02-01

The Peruvian upwelling region shows pronounced near-surface submesoscale variability including filaments and sharp density fronts. Submesoscale frontal processes can drive large vertical velocities and enhance vertical tracer fluxes in the upper ocean. The associated high temporal and spatial variability poses a large challenge to observational approaches targeting these processes. In this study the role of submesoscale processes for the ventilation of the near-coastal oxygen minimum zone off Peru is investigated. We use satellite based sea surface temperature measurements and multiple high-resolution glider observations of temperature, salinity, oxygen and chlorophyll fluorescence carried out in January and February 2013 off Peru near 14°S during active upwelling. Additionally, high-resolution regional ocean circulation model outputs (ROMS) outputs are analysed. At the beginning of our observational survey a previously upwelled, productive and highly oxygenated water body is found in the mixed layer. Subsequently, a cold filament forms and the waters are moved offshore. After the decay of the filament and the relaxation of the upwelling front, the oxygen enriched surface water is found in the previously less oxygenated thermocline suggesting the occurrence of frontal subduction. A numerical model simulation is used to analyse the evolution of Lagrangian numerical floats in several upwelling filaments, whose vertical structure and hydrographic properties agree well with the observations. The floats trajectories support our interpretation that the subduction of previously upwelled water occurs in filaments off Peru. We find that 40 - 60 % of the floats seeded in the newly upwelled water is subducted within a time period of 5 days. This hightlights the importance of this process in ventilating the oxycline off Peru.

Upwelling-derived oceanographic conditions impact growth performance and growth-related gene expression in intertidal fish.

PubMed

Fuentes, Eduardo N; Zuloaga, Rodrigo; Almarza, Oscar; Mendez, Katterinne; Valdés, Juan Antonio; Molina, Alfredo; Pulgar, Jose

2017-12-01

Growth is one of the main biological processes in aquatic organisms that is affected by environmental fluctuations such as upwelling (characterized by food-rich waters). In fish, growth is directly related with skeletal muscle increase; which represents the largest tissue of body mass. However, the effects of upwelling on growth, at the physiological and molecular level, are unknown. This study used Girella laevifrons (one of the most abundant intertidal fish in Eastern South Pacific) as a biological model, considering animals from upwelling (U) and non-upwelling (NU) areas. Here, we evaluated the effect of nutritional composition and food availability on growth performance and expression of key growth-related genes (insulin-kike growth factor 1 (igf1) and myosin heavy-chain (myhc)) and atrophy-related genes (muscle ring-finger 1 (murf1), F-box only protein 32 (atrogin-1) and BCL2/adenovirus E1B 19kDa-interacting protein 3 (bnip3)). We reported that, among zones, U fish displayed higher growth performance in response to nutritional composition, specifically between protein- and fiber-rich diets (~1g). We also found in NU fish that atrophy-related genes were upregulated with fiber-rich diet and during fasting (~2-fold at minimum respect U). In conclusion, our results suggest that the growth potential of upwelling fish may be a consequence of differential muscle gene expression. Our data provide a preliminary approach contributing on how upwelling influence fish growth at the physiological and molecular levels. Future studies are required to gain further knowledge about molecular differences between U and NU animals, as well as the possible applications of this knowledge in the aquaculture industry. Copyright © 2017 Elsevier Inc. All rights reserved.

Gradients in microbial methanol uptake: productive coastal upwelling waters to oligotrophic gyres in the Atlantic Ocean

PubMed Central

Dixon, Joanna L; Sargeant, Stephanie; Nightingale, Philip D; Colin Murrell, J

2013-01-01

Methanol biogeochemistry and its importance as a carbon source in seawater is relatively unexplored. We report the first microbial methanol carbon assimilation rates (k) in productive coastal upwelling waters of up to 0.117±0.002 d−1 (∼10 nmol l−1 d−1). On average, coastal upwelling waters were 11 times greater than open ocean northern temperate (NT) waters, eight times greater than gyre waters and four times greater than equatorial upwelling (EU) waters; suggesting that all upwelling waters upon reaching the surface (⩽20 m), contain a microbial population that uses a relatively high amount of carbon (0.3–10 nmol l−1 d−1), derived from methanol, to support their growth. In open ocean Atlantic regions, microbial uptake of methanol into biomass was significantly lower, ranging between 0.04–0.68 nmol l−1 d−1. Microbes in the Mauritanian coastal upwelling used up to 57% of the total methanol for assimilation of the carbon into cells, compared with an average of 12% in the EU, and 1% in NT and gyre waters. Several methylotrophic bacterial species were identified from open ocean Atlantic waters using PCR amplification of mxaF encoding methanol dehydrogenase, the key enzyme in bacterial methanol oxidation. These included Methylophaga sp., Burkholderiales sp., Methylococcaceae sp., Ancylobacter aquaticus, Paracoccus denitrificans, Methylophilus methylotrophus, Methylobacterium oryzae, Hyphomicrobium sp. and Methylosulfonomonas methylovora. Statistically significant correlations for upwelling waters between methanol uptake into cells and both chlorophyll a concentrations and methanol oxidation rates suggest that remotely sensed chlorophyll a images, in these productive areas, could be used to derive total methanol biological loss rates, a useful tool for atmospheric and marine climatically active gas modellers, and air–sea exchange scientists. PMID:23178665

A high-resolution Late Quaternary upwelling record from the anoxic Cariaco Basin, Venezuela

NASA Astrophysics Data System (ADS)

Peterson, L. C.; Overpeck, J. T.; Kipp, N. G.; Imbrie, J.

1991-02-01

Results are presented of a high-resolution study of the planktonic foraminiferal faunas from two piston cores recovered from the Cariaco Basin in the southern Caribbean Sea. The Cariaco Basin is a small anoxic marine basin on the northern continental margin of Venezuela in an area today characterized by both seasonal trade wind-induced upwelling and pronounced dry and wet seasons. Our data indicate that large changes in the intensity of upwelling, and hence trade wind strength, occurred in this region during the last glacial-interglacial transition and throughout the Holocene. During the last glacial lowstand of sea level, the Cariaco Basin was effectively isolated from the open Caribbean along its northern margin by the then largely emergent Tortuga Bank. Oxic conditions existed in the deep Cariaco Basin at this time, and surface productivity was low. About 12,600 years ago, the abrupt initiation of strong upwelling over the basin and the onset of permanent anoxia in the deep waters are coincident with the rapid rise of sea level that accompanied the peak interval of meltwater discharge from the Laurentide Ice Sheet into the Gulf of Mexico. Strong upwelling between 12,600 and about 10,000 years ago may be related to intensified trade winds resulting, in part, from cooler sea surface temperatures in the Caribbean and Gulf of Mexico. After about 10,000 years ago, upwelling intensity was reduced, though highly variable. A preliminary frequency domain analysis of the Holocene portion of the Cariaco Basin time series suggests that solar forcing may explain a significant component of the century-scale variability observed in the record of upwelling and trade wind strength.

Modeling the dynamical sinking of biogenic particles in eastern-boundary upwelling systems

NASA Astrophysics Data System (ADS)

Rossi, Vincent; Monroy, Pedro; López, Cristobal; Hernández-García, Emilio; Dewitte, Boris; Paulmier, Aurélien; Garçon, Véronique

2017-04-01

Although most of the organic material produced by photosynthesis in the upper ocean is recycled in surface waters, a significant portion sinks into the deep ocean where it is stored for long time-scales. Knowledge of the export flux of organic carbon from the sea surface to depths is needed to estimate the efficiency of the biological carbon pump, a key process of global carbon cycling. We study how the sinking of biogenic particles produced in the euphotic layer is affected by subsurface ocean currents as derived from a regional dynamical model. In the range of sizes and densities appropriate for marine biogenic particles, the sinking trajectories are given by the equation of motion of small particles in a fluid flow (Maxey-Riley equation). We use a modelled 3-dimensional velocity field with major energetic structures in the mesoscale and we assess the influence of physical processes such as the Coriolis force and the inertia of the particles. We find that the latter forces are negligible as compared to the most important terms, which are passive motion with the velocity of the flow and a constant added vertical velocity due to gravity. Horizontal two-dimensional clustering is observed at depth, similar to the inhomogeneities observed in sinking ocean particles. Based on ensemble experiments, we explore the influence of the mean flow and the mesoscale eddy field on particles lateral advection and size fractionation. This modeling framework allows us to extend the concept of particle source funnels and helps interpreting particles fluxes estimated from sediment traps deployed in upwelling systems, informing the spatial mismatch between surface production and particle export.

Coastal upwelling by wind-driven forcing in Jervis Bay, New South Wales: A numerical study for 2011

NASA Astrophysics Data System (ADS)

Sun, Youn-Jong; Jalón-Rojas, Isabel; Wang, Xiao Hua; Jiang, Donghui

2018-06-01

The Princeton Ocean Model (POM) was used to investigate an upwelling event in Jervis Bay, New South Wales (SE Australia), with varying wind directions and strengths. The POM was adopted with a downscaling approach for the regional ocean model one-way nested to a global ocean model. The upwelling event was detected from the observed wind data and satellite sea surface temperature images. The validated model reproduced the upwelling event showing the input of bottom cold water driven by wind to the bay, its subsequent deflection to the south, and its outcropping to the surface along the west and south coasts. Nevertheless, the behavior of the bottom water that intruded into the bay varied with different wind directions and strengths. Upwelling-favorable wind directions for flushing efficiency within the bay were ranked in the following order: N (0°; northerly) > NNE (30°; northeasterly) > NW (315°; northwesterly) > NE (45°; northeasterly) > ENE (60°; northeasterly). Increasing wind strengths also enhance cold water penetration and water exchange. It was determined that wind-driven downwelling within the bay, which occurred with NNE, NE and ENE winds, played a key role in blocking the intrusion of the cold water upwelled through the bay entrance. A northerly wind stress higher than 0.3 N m-2 was required for the cold water to reach the northern innermost bay.

On the Hiatus in the Acceleration of Tropical Upwelling Since the Beginning of the 21st Century

NASA Technical Reports Server (NTRS)

Aschmann, J.; Burrows, J. P.; Gebhardt, C.; Rozanov, A.; Hommel, R.; Weber, M.; Thompson, A. M.

2014-01-01

Chemistry-climate models predict an acceleration of the upwelling branch of the Brewer-Dobson circulation as a consequence of increasing global surface temperatures, resulting from elevated levels of atmospheric greenhouse gases. The observed decrease of ozone in the tropical lower stratosphere during the last decades of the 20th century is consistent with the anticipated acceleration of upwelling. However, more recent satellite observations of ozone reveal that this decrease has unexpectedly stopped in the first decade of the 21st century, challenging the implicit assumption of a continuous acceleration of tropical upwelling. In this study we use three decades of chemistry transport-model simulations (1980-2013) to investigate this phenomenon and resolve this apparent contradiction. Our model reproduces the observed tropical lower stratosphere ozone record, showing a significant decrease in the early period followed by a statistically robust trend-change after 2002. We demonstrate that this trend-change is correlated with corresponding changes in the vertical transport and conclude that a hiatus in the acceleration of tropical upwelling occurred during the last decade.

Geographical gradients in selection can reveal genetic constraints for evolutionary responses to ocean acidification.

PubMed

Gaitán-Espitia, Juan Diego; Marshall, Dustin; Dupont, Sam; Bacigalupe, Leonardo D; Bodrossy, Levente; Hobday, Alistair J

2017-02-01

Geographical gradients in selection can shape different genetic architectures in natural populations, reflecting potential genetic constraints for adaptive evolution under climate change. Investigation of natural pH/pCO 2 variation in upwelling regions reveals different spatio-temporal patterns of natural selection, generating genetic and phenotypic clines in populations, and potentially leading to local adaptation, relevant to understanding effects of ocean acidification (OA). Strong directional selection, associated with intense and continuous upwellings, may have depleted genetic variation in populations within these upwelling regions, favouring increased tolerances to low pH but with an associated cost in other traits. In contrast, diversifying or weak directional selection in populations with seasonal upwellings or outside major upwelling regions may have resulted in higher genetic variances and the lack of genetic correlations among traits. Testing this hypothesis in geographical regions with similar environmental conditions to those predicted under climate change will build insights into how selection may act in the future and how populations may respond to stressors such as OA. © 2017 The Author(s).

Western boundary upwelling dynamics off Oman

NASA Astrophysics Data System (ADS)

Vic, Clément; Capet, Xavier; Roullet, Guillaume; Carton, Xavier

2017-05-01

Despite its climatic and ecosystemic significance, the coastal upwelling that takes place off Oman is not well understood. A primitive-equation, regional model forced by climatological wind stress is used to investigate its dynamics and to compare it with the better-known Eastern Boundary Upwellings (EBUs). The solution compares favorably with existing observations, simulating well the seasonal cycles of thermal structure, surface circulation (mean and turbulent), and sea-surface temperature (SST). There is a 1.5-month lag between the maximum of the upwelling-favorable wind-stress-curl forcing and the oceanic response (minima in sea-surface height and SST), which we attribute to onshore-propagating Rossby waves. A southwestward-flowing undercurrent (opposite to the direction of the near-surface flow) is also simulated with a core depth of 1000 m, much deeper than found in EBUs (150-200 m). An EKE budget reveals that, in contrast to EBUs, the upwelling jet is more prone to barotropic than baroclinic instability and the contribution of locally-generated instabilities to EKE is higher by an order of magnitude. Advection and redistribution of EKE by standing mesoscale features also play a significant role in EKE budget.

On the use of the earth resources technology satellite /LANDSAT-1/ in optical oceanography

NASA Technical Reports Server (NTRS)

Maul, G. A.; Gordon, H. R.

1975-01-01

Observations of the Gulf Stream System in the Gulf of Mexico were obtained in synchronization with LANDSAT-1. Computer enhanced images, which are necessary to extract useful oceanic information, show that the current can be observed by color (diffuse radiance) or sea state (specular radiance) effects associated with the cyclonic boundary even in the absence of a surface thermal signature. The color effect relates to the spectral variations in the optical properties of the water and its suspended particles, and is studied by radiative transfer theory. Significant oceanic parameters identified are: the probability of forward scattering, and the ratio of scattering to total attenuation. Several spectra of upwelling diffuse light are computed as a function of the concentration of particles and yellow substance.

Late Neogene foraminifera from the northern Namibian continental shelf and the transition to the Benguela Upwelling System

NASA Astrophysics Data System (ADS)

Bergh, Eugene W.; Compton, John S.; Frenzel, Peter

2018-05-01

Middle Miocene to Plio-Pleistocene foraminifera provide insights into the palaeoenvironment on the northern Namibian continental shelf located at the far northern end of the present-day Benguela Upwelling System (BUS). Biostratigraphy and Strontium Isotope Stratigraphy (SIS) of the recovered basal olive-green mud unit indicate an age of 16 to 14 Ma. A sharp, erosional contact separates the basal mud from the overlying Plio-Pleistocene gravelly pelletal phosphorite sands. Grain size data, P/B ratios and benthic diversity indices indicate a change between the middle Miocene and overlying Plio-Pleistocene palaeoenvironments linked to the timing and conditions associated with the initiation of the BUS. The different lithological units and microfossil assemblages in the olive-green mud unit and the overlying pelletal phosphorite units support the late Miocene initiation of the BUS and the northwards migration of the Angola-Benguela Front. Planktic foraminifera indicate a shift from warmer surface water conditions to cooler conditions during the initiation of the BUS. Benthic palaeobathymetric ranges and P/B ratios are consistent with outer shelf water depths suggesting a deeper palaeoenvironment during the Mid-Miocene Climatic Optimum (MMCO) than today. Benthic foraminifera in the middle Miocene are dominated by large (>1 mm) taxa and adapted to oligotrophic environments before the initiation of the BUS. The benthic assemblage composition indicates that bottom water conditions changed to eutrophic conditions during the Plio-Pleistocene under intensified upwelling conditions.

Intraseasonal patterns in coastal plankton biomass off central Chile derived from satellite observations and a biochemical model

NASA Astrophysics Data System (ADS)

Gomez, Fabian A.; Spitz, Yvette H.; Batchelder, Harold P.; Correa-Ramirez, Marco A.

2017-10-01

Subseasonal (5-130 days) environmental variability can strongly affect plankton dynamics, but is often overlooked in marine ecology studies. We documented the main subseasonal patterns of plankton biomass in the coastal upwelling system off central Chile, the southern part of the Humboldt System. Subseasonal variability was extracted from temporal patterns in satellite data of wind stress, sea surface temperature, and chlorophyll from the period 2003-2011, and from a realistically forced eddy-resolving physical-biochemical model from 2003 to 2008. Although most of the wind variability occurs at submonthly frequencies (< 30 days), we found that the dominant subseasonal pattern of phytoplankton biomass is within the intraseasonal band (30-90 days). The strongest intraseasonal coupling between wind and plankton is in spring-summer, when increased solar radiation enhances the phytoplankton response to upwelling. Biochemical model outputs show intraseasonal shifts in plankton community structure, mainly associated with the large fluctuations in diatom biomass. Diatom biomass peaks near surface during strong upwelling, whereas small phytoplankton biomass peaks at subsurface depths during relaxation or downwelling periods. Strong intraseasonally forced changes in biomass and species composition could strongly impact trophodynamics connections in the ecosystem, including the recruitment of commercially important fish species such as common sardine and anchovy. The wind-driven variability of chlorophyll concentration was connected to mid- and high-latitude atmospheric anomalies, which resemble disturbances with frequencies similar to the tropical Madden-Julian Oscillation.

Cyanobacterial distributions along a physico-chemical gradient in the Northeastern Pacific Ocean.

PubMed

Sudek, Sebastian; Everroad, R Craig; Gehman, Alyssa-Lois M; Smith, Jason M; Poirier, Camille L; Chavez, Francisco P; Worden, Alexandra Z

2015-10-01

The cyanobacteria Prochlorococcus and Synechococcus are important marine primary producers. We explored their distributions and covariance along a physico-chemical gradient from coastal to open ocean waters in the Northeastern Pacific Ocean. An inter-annual pattern was delineated in the dynamic transition zone where upwelled and eastern boundary current waters mix, and two new Synechococcus clades, Eastern Pacific Clade (EPC) 1 and EPC2, were identified. By applying state-of-the-art phylogenetic analysis tools to bar-coded 16S amplicon datasets, we observed higher abundance of Prochlorococcus high-light I (HLI) and low-light I (LLI) in years when more oligotrophic water intruded farther inshore, while under stronger upwelling Synechococcus I and IV dominated. However, contributions of some cyanobacterial clades were proportionally relatively constant, e.g. Synechococcus EPC2. In addition to supporting observations that Prochlorococcus LLI thrive at higher irradiances than other LL taxa, the results suggest LLI tolerate lower temperatures than previously reported. The phylogenetic precision of our 16S rRNA gene analytical approach and depth of bar-coded sequencing also facilitated detection of clades at low abundance in unexpected places. These include Prochlorococcus at the coast and Cyanobium-related sequences offshore, although it remains unclear whether these came from resident or potentially advected cells. Our study enhances understanding of cyanobacterial distributions in an ecologically important eastern boundary system. © 2014 The Authors. Environmental Microbiology published by Society for Applied Microbiology and John Wiley & Sons Ltd.

Spectral measurements of ocean-dumped wastes tested in the marine upwelled spectral signature laboratory

NASA Technical Reports Server (NTRS)

Witte, W. G.; Usry, J. W.; Whitlock, C. H.; Gurganus, E. A.

1979-01-01

Transmission and inherent upwelled radiance measurements were made of various mixtures of three ocean-dumped industrial plant wastes in artificial seawater. Laboratory analyses were made of the physical and chemical properties of the various mixtures. These results and the laboratory measurements of beam attenuation and inherent upwelled radiance indicate a variety of chemical and spectral responses when industrial wastes are added to artificial seawater. In particular, increased levels of turbidity did not always cause increased levels of inherent reflectance.

Dynamics of plankton populations in upwelling areas

NASA Technical Reports Server (NTRS)

Szekielda, K. H. (Principal Investigator)

1975-01-01

The author has identified the following significant results. Spectral properties of the upwelled waters off the NW coast of Africa were studied with observations derived from aircraft and Skylab. Results indicate that the two-channel, ratio approach is ineffective in determining surface chlorophyll concentrations. Ocean color boundaries and temperature gradients were found to be directly correlated with each other and also with fishing effort in the upwelling region. Photographic and scanner data derived from Skylab were effective in locating ocean boundaries and mapping temperature distributions.

West Antarctic Ice Sheet retreat driven by Holocene warm water incursions

PubMed Central

Hillenbrand, Claus-Dieter; Smith, James A.; Hodell, David A.; Greaves, Mervyn; Poole, Christopher R.; Kender, Sev; Williams, Mark; Andersen, Thorbjørn Joest; Jernas, Patrycja E.; Klages, Johann P.; Roberts, Stephen J.; Gohl, Karsten; Larter, Robert D.; Kuhn, Gerhard

2017-01-01

Glaciological and oceanographic observations coupled with numerical models show that warm Circumpolar Deep Water (CDW) upwelling onto the West Antarctic continental shelf causes melting of the undersides of floating ice shelves. Because these ice shelves buttress glaciers feeding into them, their ocean-induced thinning is driving Antarctic ice-sheet loss today. Here we present the first multi-proxy data based reconstruction of variability in CDW inflow to the Amundsen Sea sector, the most vulnerable part of the West Antarctic Ice Sheet, during the last 11,000 years. The chemical composition of foraminifer shells and benthic foraminifer assemblages in marine sediments indicate that enhanced CDW upwelling, controlled by the latitudinal position of the Southern Hemisphere westerly winds, forced deglaciation of this sector both until 7,500 years ago, when an ice-shelf collapse may have caused rapid ice-sheet thinning further upstream, and since the 1940s. These results increase confidence in the predictive capability of current ice-sheet models. PMID:28682333

Eddy-Pump: Pelagic carbon pump processes along the eddying Antarctic Polar Front in the Atlantic Sector of the Southern Ocean

NASA Astrophysics Data System (ADS)

Strass, Volker H.; Wolf-Gladrow, Dieter; Pakhomov, Evgeny A.; Klaas, Christine

2017-04-01

The Southern Ocean influences earth's climate in many ways. It hosts the largest upwelling region of the world oceans where 80% of deep waters resurface (Morrison et al., 2015). A prominent feature is the broad ring of cold water, the Antarctic Circumpolar Current (ACC), which encircles the Antarctic continent and connects all other oceans. The ACC plays a major role in the global heat and freshwater transports and ocean-wide cycles of chemical and biogenic elements, and harbours a series of unique and distinct ecosystems. Due to the upwelling of deep-water masses in the Antarctic Divergence, there is high supply of natural CO2 as well as macronutrients, leading to the worldwide highest surface nutrient concentrations. Despite the ample macronutrients supply, phytoplankton concentration is generally low, limited either by low micronutrient (iron) availability, insufficient light due to deep wind-mixed layers or grazing by zooplankton, or by the combination of all, varying temporally and regionally.

Late Eocene diatomite from the Peruvian coastal desert, coastal upwelling in the eastern Pacific, and Pacific circulation before the terminal Eocene event

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marty, R.; Dunbar, R.; Martin, J.B.

1988-09-01

Previously undocumented late Eocene diatomaceous sediments are present near Fundo Desbarrancado (FD) in southern Peru. These sediments are similar to Miocene diatomite from the same area but, unlike the Miocene diatomite, the FD sediments contain cherty layers, are enriched in CaCO/sub 3/, have a diverse and abundant radiolarian fauna, and possess varved-massive and millimeter- and meter-scale biogenic-terrigenous alternations. The FD sediments are part of an Eocene sequence that includes the clastic sediments of the Paracas Formation, and they are correlative to the Chira Formation of northern Peru. The Paleogene biogenic sediments of western South America show that coastal upwelling developedmore » in the eastern Pacific before the latest Eocene, argue for the existence of a proto-Humboldt current at this time, and suggest that the terminal Eocene event was the culmination of gradual changes and not a catastrophic event at the Eocene/Oligocene boundary.« less

Ageostrophic Frontal Processes Controlling Phytoplankton Production in the Catalano-Balearic Sea (Western Mediterranean)

PubMed Central

Oguz, Temel; Macias, Diego; Tintore, Joaquin

2015-01-01

Buoyancy-induced unstable boundary currents and the accompanying retrograde density fronts are often the sites of pronounced mesoscale activity, ageostrophic frontal processes, and associated high biological production in marginal seas. Biophysical model simulations of the Catalano-Balearic Sea (Western Mediterranean) illustrated that the unstable and nonlinear southward frontal boundary current along the Spanish coast resulted in a strain-driven frontogenesis mechanism. High upwelling velocities of up to 80 m d-1 injected nutrients into the photic layer and promoted enhanced production on the less dense, onshore side of the front characterized by negative relative vorticity. Additional down-front wind stress and heat flux (cooling) intensified boundary current instabilities and thus ageostrophic cross-frontal circulation and augmented production. Specifically, entrainment of nutrients by relatively strong buoyancy-induced vertical mixing gave rise to a more widespread phytoplankton biomass distribution within the onshore side of the front. Mesoscale cyclonic eddies contributed to production through an eddy pumping mechanism, but it was less effective and more limited regionally than the frontal processes. The model was configured for the Catalano-Balearic Sea, but the mechanisms and model findings apply to other marginal seas with similar unstable frontal boundary current systems. PMID:26065688

Geodynamic constraints on deep-mantle buoyancy: Implications for thermochemical structure of LLSVP and large-scale upwellings under the Pacific Ocean.

NASA Astrophysics Data System (ADS)

Forte, A. M.; Glisovic, P.; Grand, S. P.; Lu, C.; Simmons, N. A.; Rowley, D. B.

2015-12-01

Convection-related data constrain lower-mantle density anomalies that contribute to mantle convective flow. These include global gravity and topography anomalies, plate motions and excess ellipticity of the core-mantle boundary (CMB). Each datum possesses differing wavelength and depth dependent resolution of heterogeneity and thus the strongest constraints on density anomalies are obtained by jointly inverting all data in combination. The joint-inversions employ viscous response functions (i.e. geodynamic kernels) for a flowing mantle. Non-uniqueness is greatly reduced by including seismic and mineral physics data into the joint inversions. We present the results of inversions where seismic and geodynamic data are singly and jointly inverted to map density anomalies. Employing mineral physical data we estimate thermal and compositional contributions to density anomalies. We evaluate the extent to which "Large Low Shear Velocity Provinces" (LLSVP) are anomalous and we determine their impact on the global pattern of convective flow. The inversions yield consistent maps of lower-mantle flow (see figure) that are dominated by two large upwellings, under the Western Pacific (next to the Caroline microplate) and Eastern Pacific (under the East Pacific Rise). These hot upwellings effectively delimit the margins of the Pacific LLSVP, suggesting intrinsic negative buoyancy within this structure impedes large-scale upwellings in the mantle above. These two upwellings do not resemble classical mantle "plumes" found in simple isoviscous and isochemical convection models but their contribution to mass and heat transport across the lower mantle is significant and thus behave similarly to plumes. The large scale of these upwellings may be understood in terms of the high viscosity in the lower mantle, inferred from geodynamic constraints on mantle rheology. Very-long time convection simulations initiated with present-day structure inferred from these inversions show the two Pacific upwellings possess remarkable geographic fixity and longevity extending over several hundred million years, again a consequence of the high viscosity in the lower mantle. These upwellings are fed by large heat flux across the CMB (from 12 to 20 TW) and should play a major role in the thermal evolution of the mantle.

Sea Surface Temperature Influence on Terrestrial Gross Primary Production along the Southern California Current.

PubMed

Reimer, Janet J; Vargas, Rodrigo; Rivas, David; Gaxiola-Castro, Gilberto; Hernandez-Ayon, J Martin; Lara-Lara, Ruben

2015-01-01

Some land and ocean processes are related through connections (and synoptic-scale teleconnections) to the atmosphere. Synoptic-scale atmospheric (El Niño/Southern Oscillation [ENSO], Pacific Decadal Oscillation [PDO], and North Atlantic Oscillation [NAO]) decadal cycles are known to influence the global terrestrial carbon cycle. Potentially, smaller scale land-ocean connections influenced by coastal upwelling (changes in sea surface temperature) may be important for local-to-regional water-limited ecosystems where plants may benefit from air moisture transported from the ocean to terrestrial ecosystems. Here we use satellite-derived observations to test potential connections between changes in sea surface temperature (SST) in regions with strong coastal upwelling and terrestrial gross primary production (GPP) across the Baja California Peninsula. This region is characterized by an arid/semiarid climate along the southern California Current. We found that SST was correlated with the fraction of photosynthetic active radiation (fPAR; as a proxy for GPP) with lags ranging from 0 to 5 months. In contrast ENSO was not as strongly related with fPAR as SST in these coastal ecosystems. Our results show the importance of local-scale changes in SST during upwelling events, to explain the variability in GPP in coastal, water-limited ecosystems. The response of GPP to SST was spatially-dependent: colder SST in the northern areas increased GPP (likely by influencing fog formation), while warmer SST at the southern areas was associated to higher GPP (as SST is in phase with precipitation patterns). Interannual trends in fPAR are also spatially variable along the Baja California Peninsula with increasing secular trends in subtropical regions, decreasing trends in the most arid region, and no trend in the semi-arid regions. These findings suggest that studies and ecosystem process based models should consider the lateral influence of local-scale ocean processes that could influence coastal ecosystem productivity.

Sea Surface Temperature Influence on Terrestrial Gross Primary Production along the Southern California Current

PubMed Central

Reimer, Janet J.; Vargas, Rodrigo; Rivas, David; Gaxiola-Castro, Gilberto; Hernandez-Ayon, J. Martin; Lara-Lara, Ruben

2015-01-01

Some land and ocean processes are related through connections (and synoptic-scale teleconnections) to the atmosphere. Synoptic-scale atmospheric (El Niño/Southern Oscillation [ENSO], Pacific Decadal Oscillation [PDO], and North Atlantic Oscillation [NAO]) decadal cycles are known to influence the global terrestrial carbon cycle. Potentially, smaller scale land-ocean connections influenced by coastal upwelling (changes in sea surface temperature) may be important for local-to-regional water-limited ecosystems where plants may benefit from air moisture transported from the ocean to terrestrial ecosystems. Here we use satellite-derived observations to test potential connections between changes in sea surface temperature (SST) in regions with strong coastal upwelling and terrestrial gross primary production (GPP) across the Baja California Peninsula. This region is characterized by an arid/semiarid climate along the southern California Current. We found that SST was correlated with the fraction of photosynthetic active radiation (fPAR; as a proxy for GPP) with lags ranging from 0 to 5 months. In contrast ENSO was not as strongly related with fPAR as SST in these coastal ecosystems. Our results show the importance of local-scale changes in SST during upwelling events, to explain the variability in GPP in coastal, water-limited ecosystems. The response of GPP to SST was spatially-dependent: colder SST in the northern areas increased GPP (likely by influencing fog formation), while warmer SST at the southern areas was associated to higher GPP (as SST is in phase with precipitation patterns). Interannual trends in fPAR are also spatially variable along the Baja California Peninsula with increasing secular trends in subtropical regions, decreasing trends in the most arid region, and no trend in the semi-arid regions. These findings suggest that studies and ecosystem process based models should consider the lateral influence of local-scale ocean processes that could influence coastal ecosystem productivity. PMID:25923109

Constraining Seasonal and Vertical Distributions of Planktonic Foraminifera for Paleoclimate Reconstruction Since MIS3 at the Axial Seamount, Juan de Fuca Ridge

NASA Astrophysics Data System (ADS)

Chen, S. L.; Ravelo, A. C.; Clague, D. A.

2015-12-01

The California Current is an upwelling region with dynamic interactions between circulation, biological productivity and ecology. A 77 cm piston push core was taken from the Juan de Fuca Ridge Axial Seamount using a Remotely Operated Vehicle (ROV) (2213m, 45.55º N, 130.08º W), an active submarine volcano ~480 km off Oregon's coast. Five radiocarbon dates indicate that the sediment ranges from 42.6 ka at 77 cm to 17.6 ka at 15 cm, with an average sediment accumulation rate of 2.47 cm/ka from 77-15 cm, and an average rate of 0.85 cm/ka during the postglacial period (<17.6 ka). Multiple species of planktic foraminifera from the core representing subtropical, subartic, and arctic fauna have been used to constrain changes in vertical and seasonal temperature since Marine Isotope Stage 3 (MIS3). Measurements of δ18O of the upwelling species Globigerina bulloides, the thermocline dwelling species Neogloboquadrina dutertrei, and the warm mixed-layer species Orbulina universa are offset from each other, reflecting vertical and seasonal variation among the planktonic foraminifera. Of the three species, G. bulloides shows the least variation in δ18O, possibly indicating that marked changes in temperature are masking changes in the δ18O of seawater due to global ice volume changes. G. bulloides and O. universa δ18O values are similar in MIS 3 and diverge with time, indicating the development of strong seasonal succession of species, since the last glacial maximum. Bulk nitrogen isotopes and nitrogen flux provide additional constraints on upwelling strength and insight into local biological productivity and nutrient dynamics. Obtaining Mg/Ca data will clarify the δ 18O interpretation except deep in the core where metal-bearing authigenic precipitates affect Mg concentrations. These climatic proxies together provide insight into how global climate change and local seamount volcanism impacts regional productivity in the California Current.

Time scales of pattern evolution from cross-spectrum analysis of advanced very high resolution radiometer and coastal zone color scanner imagery

NASA Technical Reports Server (NTRS)

Denman, Kenneth L.; Abbott, Mark R.

1994-01-01

We have selected square subareas (110 km on a side) from coastal zone color scanner (CZCS) and advanced very high resolution radiometer (AVHRR) images for 1981 in the California Current region off northern California for which we could identify sequences of cloud-free data over periods of days to weeks. We applied a two-dimensional fast Fourier transformation to images after median filtering, (x, y) plane removal, and cosine tapering. We formed autospectra and coherence spectra as functions of a scalar wavenumber. Coherence estimates between pairs of images were plotted against time separation between images for several wide wavenumber bands to provide a temporal lagged coherence function. The temporal rate of loss of correlation (decorrelation time scale) in surface patterns provides a measure of the rate of pattern change or evolution as a function of spatial dimension. We found that patterns evolved (or lost correlation) approximately twice as rapidly in upwelling jets as in the 'quieter' regions between jets. The rapid evolution of pigment patterns (lifetime of about 1 week or less for scales of 50-100 km) ought to hinder biomass transfer to zooplankton predators compared with phytoplankton patches that persist for longer times. We found no significant differences between the statistics of CZCS and AVHRR images (spectral shape or rate of decorrelation). In addition, in two of the three areas studied, the peak correlation between AVHRR and CZCS images from the same area occurred at zero lag, indicating that the patterns evolved simutaneously. In the third area, maximum coherence between thermal and pigment patterns occurred when pigment images lagged thermal images by 1-2 days, mirroring the expected lag of high pigment behind low temperatures (and high nutrients) in recently upwelled water. We conclude that in dynamic areas such as coastal upwelling systems, the phytoplankton cells (identified by pigment color patterns) behave largely as passive scalars at the mesoscale and that growth, death, and sinking of phytoplankton collectively play at most a mariginal role in determining the spectral statistics of the pigment patterns.

Alkenone radiocarbon stratigraphy at high resolution continental marigin sites

NASA Astrophysics Data System (ADS)

Mollenhauer, G.; Eglinton, T.; Freudenthal, T.; Lamy, F.

2003-04-01

Radiocarbon stratigraphy is an essential tool for high resolution Late Quaternary paleoceanographic studies. For this purpose, radiocarbon ages of foraminifera have been extensively measured. Age models based on these measurements are commonly applied to a wide range of sediment proxy information, including the investigation of temporal leads and lags. The critical assumption made in these studies is that temporal coupling between foraminifera and other sediment constituents, including specific biomarkers of marine phytoplankton, e.g. alkenones, is maintained in the sediments. A recent study using coupled foraminifera and alkenone ages was conducted at a high sedimentation rate site situated at the Bermuda Rise sediment drift body. Ages of formanifera and alkenones differed by up to 8000 years. As an interpreation of these data, it was suggested that sediment constituents residing in different grain size fractions may have different current transport properties and may thus originate from different source areas separated by large geographical distances. Sediment retrieved from a site influenced by lateral advection would thus have to be regarded as a mixture of material from different sources. The time span between production and final deposition may be site dependent and remains largely unknown. Continental margins underlying high productivity areas are sites of high sediment accumulation. The major part of this sediment is believed to be biogenic and is produced in the overlying water column. Sediment particles are expected to be deposited rapidly at or near the site of production regardless of their size. To evaluate this premise, we have measured coupled radiocarbon ages of foraminifera, TOC and alkenones in samples taken from sediment cores retreived from three continental margin high accumulation rate sites. Cores from the Benguela upwelling system, the North West African upwelling system and from the Chilean margin high productivity area were chosen. All sites are characterized by high sedimentation rates (>15 cm/kyr). Variable current regimes prevailing at the individual sites may provide insight as to the factors controlling the sedimentation of fine grained particles as well as concerning source areas and residence time in bottom nepheloid layers. Paired foraminifera and alkenone ages provide important constraints on the interpretation of the proxy data obtained from each of the proxy carriers. In the future, alkenone temperatures combined with alkenone ages may thus also contribute to reconstruction of current regimes and trajectories.

Coral-inferred Variability of Upstream Kuroshio Current from 1953-2004 AD

NASA Astrophysics Data System (ADS)

Li, X.; Yi, L.; Shen, C. C.; Hsin, Y. C.

2016-12-01

The Kuroshio Current (KC), one of the most important western boundary currents in the North Pacific Ocean, strongly impacts regional climate in East Asia and upper-ocean thermal structure. However, the responses of KC to regional and remote climate forcing are poorly understood owing to lacking of long-term KC observations. Here, we present a sea surface temperature (SST) record from 1953 to 2004 AD derived from monthly skeletal δ18O data of a living coral Porites core, drilled in Nanwan, southern Taiwan (22°N, 121°E), located on the western front of the Upstream KC. The increased/reduced Kuroshio transport would generate stronger/weaker upwelling in Southern Taiwan, which can cause lower/higher SST. Agreement between dynamics of interannual coral δ18O and modern KC data shows that the regional coral δ18O can be used as a promising proxy for Upstream KC intensity. The KC-induced SST anomaly record reveals prominent interannual and decadal variability predominantly controlled by the bifurcation latitude of North Equatorial Current. We also find that the reconstructed KC intensity at east of Taiwan and south of Japan have nearly simultaneous interannual changes, suggesting the same dominant forcing(s) for the entire KC system. Additional work is needed to understand the KC system with respect to the interannual to decadal climate variability and the influences of global warming.

Resuspension and Shelf-Deep Ocean Exchange in the Northern California Current: New Insights From Underwater Gliders

NASA Astrophysics Data System (ADS)

Erofeev, A.; Barth, J. A.; Shearman, R. K.; Pierce, S. D.

2016-02-01

Shelf-deep ocean exchange is dominated by wind-driven upwelling and downwelling in the northern California Current. The interaction of strong, along-shelf jets with coastline and bottom topographic features can also create significant cross-margin exchange. We are using data from over 60,000 kilometers of autonomous underwater glider tracks to understand the temporal and spatial distribution of shelf-deep ocean exchange off central Oregon. Year-round glider observations of temperature, salinity, depth-averaged currents, chlorophyll fluorescence, light backscatter, and colored dissolved organic matter fluorescence from a single cross-margin transect are used to examine shelf-deep ocean exchange mechanisms. During summer, cross-margin exchange is dominated by wind-driven upwelling and the relaxation or reversal of the dominant southward winds. This process has been fairly well observed and studied due to the relatively low sea states and winds during summer. There is far less data from fall and winter off Oregon, a time of strong winds and large waves. We use autonomous underwater gliders to sample during the winter, including through the fall and spring transitions. Glider observations of suspended material detected via light backscatter, show time-space variations in resuspension in the bottom boundary layer due to winds, waves and currents. Examples of shelf-deep ocean exchange are shown by layers with high light backscatter separating from the bottom near the shelf break and extending into the interior along isopycnals. We describe these features and events in relationship to wind-forcing, along-shelf flows, and other forcing mechanisms.

Can Vertical Migrations of Dinoflagellates Explain Observed Bioluminescence Patterns During an Upwelling Event in Monterey Bay, California?

DTIC Science & Technology

2012-01-25

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Changes in optical characteristics of surface microlayers hint to photochemically and microbially-mediated DOM turnover in the upwelling region off Peru

NASA Astrophysics Data System (ADS)

Galgani, L.; Engel, A.

2015-12-01

The coastal upwelling system off Peru is characterized by high biological activity and a pronounced subsurface oxygen minimum zone, as well as associated emissions of atmospheric trace gases such as N2O, CH4 and CO2. During the Meteor (M91) cruise to the Peruvian upwelling system in 2012, we investigated the composition of the sea-surface microlayer (SML), the oceanic uppermost boundary directly subject to high solar radiation, often enriched in specific organic compounds of biological origin like Chromophoric Dissolved Organic Matter (CDOM) and marine gels. In the SML, the continuous photochemical and microbial recycling of organic matter may strongly influence gas exchange between marine systems and the atmosphere. In order to understand organic matter cycling in surface films, we analyzed SML and underlying water samples at 38 stations determining DOC concentration, amino acid composition, marine gels, CDOM and bacterial and phytoplankton abundance as indicators of photochemical and microbial alteration processes. CDOM composition was characterized by spectral slope (S) values and Excitation-Emission Matrix fluorescence (EEMs), which allow to track changes in molecular weight (MW) of DOM, and to determine potential DOM sources and sinks. We identified five fluorescent components of the CDOM pool, of which two had excitation/emission characteristics of protein-like fluorophores and were highly enriched in the SML. CDOM composition and changes in spectral slope properties suggested a local microbial release of HMW DOM directly in the SML as a response to light exposure in this extreme environment. Our results suggest that microbial and photochemical processes play an important role for the production, alteration and loss of optically active substances in the SML.

Metal Deposition Along the Peru Margin Since the Last Glacial Maximum: Evidence For Regime Change at \\sim 6ka

NASA Astrophysics Data System (ADS)

Tierney, J.; Cleaveland, L.; Herbert, T.; Altabet, M.

2004-12-01

The Peru Margin upwelling zone plays a key role in regulating marine biogeochemical cycles, particularly the fate of nitrate. High biological productivity and low oxygen waters fed into the oxygen minimum zone result in intense denitrification in the modern system, the consequences of which are global in nature. It has been very difficult, however, to study the paleoclimatic history of this region because of the poor preservation of carbonate in Peru Margin sediments. Here we present records of trace metal accumulation from two cores located in the heart of the suboxic zone off the central Peru coast. Chronology comes from multiple AMS 14C dates on the alkenone fraction of the sediment, as well as correlation using major features of the \\delta 15N record in each core. ODP Site 1228 provides a high resolution, continuous sediment record from the Recent to about 14ka, while gravity core W7706-41k extends the record to the Last Glacial Maximum. Both cores were sampled at a 100 yr resolution, then analyzed for % N, \\delta 15N, alkenones, and trace metal concentration. Analysis of redox-sensitive metals (Mo and V) alongside metals associated with changes in productivity (Ni and Zn) provides perspective on the evolution of the upwelling system and distinguishes the two major factors controlling the intensity of the oxygen minimum zone. The trace metal record exhibits a notable increase in the intensity and variability of low oxygen waters and productivity beginning around 6ka and extending to the present. Within this most recent 6ka interval, the data suggest fluctuations in oxygenation and productivity occur on 1000 yr timescales. Our core records, therefore, suggest that the Peru Margin upwelling system strengthened significantly during the mid to late Holocene.

Comparison of shelf currents off central California prior to and during the 1997-1998 El Nino

USGS Publications Warehouse

Ryan, H.F.; Noble, M.A.

2005-01-01

Moored current, temperature, salinity, and pressure data were collected at three sites that transect the narrow continental shelf offshore of Davenport, CA, starting in August 1996 and continuing to the spring of 1998. This data set allowed a comparison of oceanographic conditions prior to (8/96-3/97) and during (8/97-3/98) the last major El Nin??o. During this El Nin??o, mean temperatures over the 8-month time period were about 3??C warmer than during the prior year at all of the sites. Correlations between near-surface and near-bottom temperatures, and between near-surface temperature and wind stress decreased during the El Nin??o compared to conditions the year before. The mean alongshore currents were more strongly poleward during El Nin??o at sites over the mid-shelf and near the shelf break. There was a general tendency for the energy in alongshore currents to move toward lower frequencies during the El Nin??o, particularly at the sites farther offshore. The processes that forced the shelf flows changed in relative importance throughout the study. The local alongshore wind stress was less important in driving shelf currents during the El Nin??o when much of the wind-induced upwelling was confined to less than 5 km of the coast. The observed strong poleward shelf currents on the mid- to outer-shelf were not clearly tied to local forcing, but were remotely driven, most likely by slope currents. The response of the Davenport shelf to an El Nin??o event may differ from other areas since the shelf is narrow, the wind forcing is weaker than areas to the north and south, and the shelf may be at times isolated by fronts that form at strong upwelling centers. In the winter, strong storm-related winds are important in driving currents at periods not only in the synoptic wind band, but also for periods on the order of 20 d and longer.

Weakened stratospheric quasibiennial oscillation driven by increased tropical mean upwelling.

PubMed

Kawatani, Yoshio; Hamilton, Kevin

2013-05-23

The zonal wind in the tropical stratosphere switches between prevailing easterlies and westerlies with a period of about 28 months. In the lowermost stratosphere, the vertical structure of this quasibiennial oscillation (QBO) is linked to the mean upwelling, which itself is a key factor in determining stratospheric composition. Evidence for changes in the QBO have until now been equivocal, raising questions as to the extent of stratospheric circulation changes in a global warming context. Here we report an analysis of near-equatorial radiosonde observations for 1953-2012, and reveal a long-term trend of weakening amplitude in the zonal wind QBO in the tropical lower stratosphere. The trend is particularly notable at the 70-hectopascal pressure level (an altitude of about 19 kilometres), where the QBO amplitudes dropped by roughly one-third over the period. This trend is also apparent in the global warming simulations of the four models in the Coupled Model Intercomparison Project Phase 5 (CMIP5) that realistically simulate the QBO. The weakening is most reasonably explained as resulting from a trend of increased mean tropical upwelling in the lower stratosphere. Almost all comprehensive climate models have projected an intensifying tropical upwelling in global warming scenarios, but attempts to estimate changes in the upwelling by using observational data have yielded ambiguous, inconclusive or contradictory results. Our discovery of a weakening trend in the lower-stratosphere QBO amplitude provides strong support for the existence of a long-term trend of enhanced upwelling near the tropical tropopause.

Resource use of an aquacultured shellfish in the reverse estuary Bahía San Quintín, Baja California, México

NASA Astrophysics Data System (ADS)

Wilkinson, G. M.; Emery, K.; Camacho-Ibar, V.; Pace, M.; McGlathery, K.; Sandoval Gil, J.; Hernandez-Lopez, J.

2016-02-01

Shellfish aquaculture is prominent in many coastal and estuarine environments. Filter feeding by cultured shellfish connects the benthic and pelagic environments in coastal ecosystems. Bahía San Quintín is a reverse estuary in Baja California, Mexico, where Pacific oysters (Crassostrea gigas) are cultivated. While oysters likely feed heavily on phytoplankton especially during upwelling periods, we hypothesized that other forms of organic matter available in high quantities such as seagrass (Zostera marina) and macroalgae (Ulva spp.) must also be used by the oysters, especially in the most inshore portions of the bay. We measured the carbon and hydrogen stable isotope composition of oysters and their potential food resources at upper, mid, and lower bay sites during upwelling and non-upwelling seasons and applied a Bayesian mixing model to evaluate resource use. Hydrogen isotopes provided a large separation between potential food resources. Although we did not find any strong seasonal effects due to upwelling, there was a strong spatial gradient in resource use. Phytoplankton were most important at the lower (oceanic) site (median resource use for two sampling times, 68 and 79 %) and decreased up the estuary as macroalgae became more important (43 and 56 % at the upper site). At all sites for both sampling times, seagrass was an unimportant resource for oysters. The contrast between high phytoplankton use at the lower site and increased macroalgal use at the upper site is likely due to available resource biomass. Our results illustrate the adaptability of oysters to varying resource availability and the possibility of a higher system carrying capacity than that based on phytoplankton alone given multiple potential food sources.

Impacts of ENSO on air-sea oxygen exchange: Observations and mechanisms

NASA Astrophysics Data System (ADS)

Eddebbar, Yassir A.; Long, Matthew C.; Resplandy, Laure; Rödenbeck, Christian; Rodgers, Keith B.; Manizza, Manfredi; Keeling, Ralph F.

2017-05-01

Models and observations of atmospheric potential oxygen (APO ≃ O2 + 1.1 * CO2) are used to investigate the influence of El Niño-Southern Oscillation (ENSO) on air-sea O2 exchange. An atmospheric transport inversion of APO data from the Scripps flask network shows significant interannual variability in tropical APO fluxes that is positively correlated with the Niño3.4 index, indicating anomalous ocean outgassing of APO during El Niño. Hindcast simulations of the Community Earth System Model (CESM) and the Institut Pierre-Simon Laplace model show similar APO sensitivity to ENSO, differing from the Geophysical Fluid Dynamics Laboratory model, which shows an opposite APO response. In all models, O2 accounts for most APO flux variations. Detailed analysis in CESM shows that the O2 response is driven primarily by ENSO modulation of the source and rate of equatorial upwelling, which moderates the intensity of O2 uptake due to vertical transport of low-O2 waters. These upwelling changes dominate over counteracting effects of biological productivity and thermally driven O2 exchange. During El Niño, shallower and weaker upwelling leads to anomalous O2 outgassing, whereas deeper and intensified upwelling during La Niña drives enhanced O2 uptake. This response is strongly localized along the central and eastern equatorial Pacific, leading to an equatorial zonal dipole in atmospheric anomalies of APO. This dipole is further intensified by ENSO-related changes in winds, reconciling apparently conflicting APO observations in the tropical Pacific. These findings suggest a substantial and complex response of the oceanic O2 cycle to climate variability that is significantly (>50%) underestimated in magnitude by ocean models.

Changing surface water conditions for the last 500 ka in the Southeast Atlantic: Implications for variable influences of Agulhas leakage and Benguela upwelling

NASA Astrophysics Data System (ADS)

Petrick, Benjamin F.; McClymont, Erin L.; Marret, Fabienne; van der Meer, Marcel T. J.

2015-09-01

The Southeast Atlantic Ocean is an important component of global ocean circulation, as it includes heat and salt transfer into the Atlantic through the Agulhas leakage as well as the highly productive Benguela upwelling system. Here we reconstruct sea surface temperatures (SSTs) from Ocean Drilling Program (ODP) Site 1087 in the Southeast Atlantic to investigate surface ocean circulation patterns during the late Pleistocene (0-500 ka). The UK'37 index and dinoflagellate cyst assemblages are used to reconstruct SSTs, δDalkenone is used to reconstruct changes in sea surface salinity, and mass accumulation rates of alkenones and chlorine pigments are quantified to detect changing marine export productivity. The greatest amplitude of SST warming precedes decreases in benthic δ18O and therefore occurs early in the transition from glacials to interglacials. The δDalkenone, as a salinity indicator, increases before SSTs, suggesting that the pattern of Agulhas leakage is more complex than suggested by SST proxies. Marine isotope stage (MIS) 10 shows an anomalous pattern: it is marked by a pronounced increase in chlorine concentration, which may be related to enhanced/expanded Benguela upwelling reaching the core site. We find no evidence of an absence of Agulhas leakage throughout the record, suggesting that there is no Agulhas cutoff even during MIS 10. Finally, the ODP Site 1087 record shows an increasing strength of Agulhas leakage towards the present day, which may have impacted the intensity of the Atlantic meridional overturning circulation. As a result, the new analyses from ODP Site 1087 demonstrate a complex interaction between influences of the Benguela upwelling and the Agulhas leakage through the late Pleistocene, which are inferred here to reflect changing circulation patterns in the Southern Ocean and in the atmosphere.

Recent decadal trends in Iberian water vapour: GPS analysis and WRF process study

NASA Astrophysics Data System (ADS)

Miranda, Pedro M. A.; Nogueira, Miguel; Semedo, Alvaro; Benevides, Pedro; Catalao, Joao; Costa, Vera

2016-04-01

A 24-year simulation of the recent Iberian climate, using the WRF model at 9km resolution forced by ERA-Interim reanalysis (1989-2012), is analysed for the decadal evolution of the upwelling forcing coastal wind and for column integrated Precipitable water vapour (PWV). Results indicate that, unlike what was found by Bakun et al. (2009) for the Peruvian region, a statistically significant trend in the upwelling favourable (northerly) wind has been accompanied by a corresponding decrease in PWV, not only inland but also over the coastal waters. Such increase is consistent with a reinforced northerly coastal jet in the maritime boundary layer contributing to atmospheric Ekman pumping of dry continental air into the coastal region. Diagnostics of the prevalence of the Iberian thermal low following Hoinka and Castro (2003) also show a positive trend in its frequency during an extended summer period (April to September). These results are consistent with recent studies indicating an upward trend in the frequency of upwelling in SW Iberia (Alves and Miranda 2013), and may be relevant for climate change applications as an increase in coastal upwelling (Miranda et al 2013) may lead to substantial regional impacts in the subtropics. The same analysis with ERA-Interim reanalysis data, which was used to force the WRF simulations, does not reveal the same signal in PWV, and indeed correlates poorly with the GPS observations, indicating that the data assimilation process makes the water vapour data in reanalysis unusable for climate change purposes. The good correlation between the WRF simulated data and GPS observations allow for a detailed analysis of the processes involved in the evolution of the PWV field. Akcnowledgements: Study done within FCT Grant RECI/GEO-MET/0380/2012, financially supported by FCT Grant UID/ GEO/50019/2013-IDL Alves JMR, Miranda PMA (2013) Variability of Iberian upwelling implied by ERA-40 and ERA-Interim reanalyses, Tellus A 2013, http://dx.doi.org/10.3402/tellusa.v65i0.19245. Bakun et al (2010) Greenhouse gas, upwelling-favorable winds, and the future of coastal ocean upwelling ecosystems, Global Change Biology, doi: 10.1111/j.1365-2486.2009.02094.x Hoinka KP, Castro M (2003) The Iberian Peninsula thermal low. QJRMS, 129, 1491- 1511, doi: 10.1256/qj.01.189. Miranda et al (2013) Climate change and upwelling: response of Iberian upwelling to atmospheric forcing in a regional climate scenario. Climate Dynamics, doi: 10.1007/s00382-012-1442-9.

Paleo-climate changes during Termination V off Iberia as revealed by coccoliths assemblages

NASA Astrophysics Data System (ADS)

Palumbo, Eliana; Ornella Amore, Filomena; Flores, José-Abel; Volker, Antje

2010-05-01

Several glacial-interglacial cycles occurred during the Pleistocene separated by shorter or longer transitional periods in which the climatic system structure was modified. Termination V (425.1 -431.2 ka) is one of the largest glacial to interglacial transition of the middle Pleistocene (Voelker et al., 2009). It represents the transitional period between the glacial stage MIS 12 and the interglacial stage MIS 11. The study of Termination V represents a key to understand the dynamics causing the installation of the warm conditions of the MIS 11, a warm period considerated to be an analogue of the actual interglacial stage (Bauch et al., 2000; Hodell et al., 2000; Droxler et al., 2000; Raynaud et al.,2005; Voelker et al., 2009). In this work deep-sea core MD03-2699 (39°02.20'N, 10°39.63'W) has been studied. Modern surface waters at the site derive from the Gulf Stream and the North Atlantic Current (NAC) and are transported to the western Iberian Peninsula by two currents, the Portugal Current (PC) and the Azores Current (AzC). Hydrographic conditions of the area are influenced, during the summer, by the southward flowing PC and the upwelling filaments off Cape Roca and Peniche. During the winter the PC is displaced further offshore by the Iberian Poleward Current, which transports subtropical surface and subsurface waters, of the Azores front, northwards to the site (Peliz et al., 2005, Fiúza, 1984; Alvarez-Salgado et al., 2003). The study area is an upwelling region where phytoplankton blooms occurred in the past. Coccolithophores are a special phytoplankton group living today at all latitude regions within the photic zone (0-200 m) (Winter & Siesser, 1994). They are sensitive indicators of environmental conditions, because they directly depend on temperature, salinity and nutrients as well as the availability of sunlight (McIntyre and Bé, 1967; Giradeau et al., 1993; Winter & Siesser, 1994; Baumann & Freitag, 2004). Therefore coccolithophores quickly respond to fluctuations in climate as well as changes in surface-water conditions (Baumann & Freitag, 2004). Site MD03-2699 is located in a region where several different currents of the Northern Hemisphere came together influencing temperature and nutrient concentrations during glacial-interglacial stages. Thus this site is in a key-position to reconstruct the impact of the Mid-Pleistocene forcing on the Portuguese upwelling system and the North Atlantic's transitional waters. In this work coccolith assemblages have been studied in order to understand the differences established off Portugal within phytoplankton structure and to reconstruct environmental and paleoceanographic conditions established during Termination V. References: Bauch, H.A., Erlenkeuser, H., Helmke, J.P., Struck, U., 2000. Global Planetary Change 24: 27-39. Baumann, K.-H., and Freitag, T., 2004. Marine Micropaleontology 52: 195-215. Droxler, A.W., Bruce, C.H., Sager, W.W., Watkins, D.H., 1988Proceedings of the Ocean Drilling Program, Scientific Results 101: 221-244. Giraudeau, J., Monteiro, P.M.S., Nikodemus, K., 1993. Mar. Micropalaeontol. 22: 93- 110. Hodell, D. A., Charles, C. D., Ninnemann, U. S., 2000. Global and Planetary Change 24: 7-26. McIntyre, A., and Bè, A.H.W., 1967. Deep-Sea Res. 14, pp. 561-597. Raynaud, D., Barnola, J.M., Souchez, R., Lorrain, R., Petit, J.R., Duval, P., Lipenkov, V.Y., 2005. Nature 436: 39-40. Voelker, A. H. L. , Rodrigues, T., Stein, R., Hefter, J., Billups, K., Oppo, D., McManus, J., And Grimalt, J. O., 2009. Clim. Past Discuss., 5: 1-55. Winter, A., and Siesser, W., 1994. Cambridge University Press Cambridge 242p.

Pleistocene Variations in Delivery and Deposition of Organic Matter Under the Benguela Current Upwelling System - Biomarker Isotopic Evidence From Sediment Light-Dark Color Cycles

NASA Astrophysics Data System (ADS)

Meyers, P. A.; Bouloubassi, I.; Pancost, R. D.; Robinson, R. S.

2007-12-01

The light-dark color cycles that are distinctive features of sediment beneath the Benguela Current Upwelling System imply repetitive alternations in organic matter delivery and deposition. Organic geochemical proxies for paleoproductivity and for depositional conditions were employed to investigate the paleoceanographic processes involved in creating these cycles in two sediment sequences from ODP Site 1084 corresponding to 0.7 and 1.1 Mya. Concentrations of total organic carbon (TOC) vary between 3.5 and 17.1 wt percent, and those of calcium carbonate fluctuate inversely between 68 and 1 percent, suggesting that carbonate dissolution is involved with the light-dark cycles. Bulk organic del 13C and del 15N values that remain constant across the two light-dark sediment intervals indicate that the extent of nutrient utilization did not change in each cycle. Biomarker compositions in both sequences reflect a range of organic matter sources. Abundant n-alkanes and n-alkanols with odd-over-even and even-over-odd distributions, respectively, record land-plant inputs. Other terrestrial biomakers (e.g triterpenoid acids and alcohols) are present but in very low abundances, suggesting that the n- alkyl components derive predominantly from eolian inputs. Carbon isotopic values of n-alkanes range from -25 to -28 permil, suggesting a mixture of C3 and C4 sources. In contrast, n-alkanol isotopic compositions range from -28 to -34 permil, suggesting that they derive solely from C3 plants. Algal biomarkers are abundant and diverse, represented by 1,15-C30 diols (eustigmatophytes), 4-desmethyl and -methylsterols (diatoms, dinoflagellates), and alkenones (haptophytes). These compounds all have del 13C values ranging from ca. -22 to -24 permil, consistent with a marine origin. Systematic differences in isotopic values imply that marine productivity at 1.1 Mya was higher than at 0.7 Mya, but alkenone-based sea-surface temperatures are higher at 1.1 Mya (21 deg) than at 0.7 Mya (15 deg), which indicates that changes in water-mass properties were also involved.

Internal structure of the upwelling events at Punta Gallinas (Colombian Caribbean) from modis-sst imagery

NASA Astrophysics Data System (ADS)

Alonso, J.; Blázquez, E.; Isaza-Toro, E.; Vidal, J.

2015-10-01

The upwelling at Punta Gallinas in the Guajira Peninsula (Colombian Caribbean) was studied from the point of view of the Mathematical Morphology using 10 years of monthly composite MODIS-SST imagery. Among all the morphological operators, the skeleton is widely used to compute the axis of the of the SST fields for the observed upwelling events. The skeleton is characterized by means of the Geometrical Theory of Measurement using the fractal dimension. The upwelling in the area is driven by the dynamic of the ITCZ (InterTropical Convergence Zone) and the relationship between the area and the East-West component of the trade winds has a lag of about 4 months. It has been found that the fractal dimension of the skeleton and the area of the upwelling are related. Some relationship was found between the fractal dimension of the skeleton (its complexity) and the Southern Oscillation Index by means of linear regression and cross-spectral analysis finding coherent energy at 1 year, 6 months and in the low frequency band. Finally, a sensitivity analysis between fractal dimension and threshold SST points out to take an extreme care at the time of fixing the last one.

Phytoplankton succession in an isolated upwelled Benguela water body in relation to different initial nutrient conditions

NASA Astrophysics Data System (ADS)

Wasmund, Norbert; Nausch, Günther; Hansen, Anja

2014-11-01

Freshly upwelled water is poor in phytoplankton biomass but rich in nutrients. With its ageing, phytoplankton biomass increases whereas the nutrients are consumed. The overall aim of our investigation was to check the succession in the phytoplankton composition as a consequence of changing nutrient conditions. The experiments were carried out in mesocosms filled with surface water in the northern Benguela region and installed on board of R/V "Maria S. Merian". In the freshly upwelled water, phytoplankton took up nitrogen at a higher rate than phosphorus if compared with the Redfield ratio. Therefore, nitrogen was exhausted already by day 6. Nitrogen limitation after day 6 was indicated by decreasing chlorophyll a (chla) concentrations, primary production rates and productivity indices and increasing C/N ratios in particulate matter. Despite nitrogen limitation, phosphorus addition stimulated further growth, mainly of diatoms, pointing to luxury uptake. Cyanobacteria did not develop and nitrogen fixation was zero even with phosphorus and iron addition. Diatoms stay the most important group in the freshly upwelled water, but autotrophic and heterotrophic dinoflagellates increase strongly in the matured upwelled water. Mesocosms excluded disturbances by advective water transports, which influence the study of succssions under field conditions.

Oceanographic and atmospheric conditions on the continental shelf north of the Monterey Bay during August 2006

NASA Astrophysics Data System (ADS)

Ramp, Steven R.; Lermusiaux, Pierre F. J.; Shulman, Igor; Chao, Yi; Wolf, Rebecca E.; Bahr, Frederick L.

2011-09-01

A comprehensive data set from the ocean and atmosphere was obtained just north of the Monterey Bay as part of the Monterey Bay 2006 (MB06) field experiment. The wind stress, heat fluxes, and sea surface temperature were sampled by the Naval Postgraduate School's TWIN OTTER research aircraft. In situ data were collected using ships, moorings, gliders and AUVs. Four data-assimilating numerical models were additionally run, including the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS ®) model for the atmosphere and the Harvard Ocean Prediction System (HOPS), the Regional Ocean Modeling System (ROMS), and the Navy Coastal Ocean Model (NCOM) for the ocean. The scientific focus of the Adaptive Sampling and Prediction Experiment (ASAP) was on the upwelling/relaxation cycle and the resulting three-dimensional coastal circulation near a coastal promontory, in this case Point Año Nuevo, CA. The emphasis of this study is on the circulation over the continental shelf as estimated from the wind forcing, two ADCP moorings, and model outputs. The wind stress during August 2006 consisted of 3-10 day upwelling favorable events separated by brief 1-3 day relaxations. During the first two weeks there was some correlation between local winds and currents and the three models' capability to reproduce the events. During the last two weeks, largely equatorward surface wind stress forced the sea surface and barotropic poleward flow occurred over the shelf, reducing model skill at predicting the circulation. The poleward flow was apparently remotely forced by mesoscale eddies and alongshore pressure gradients, which were not well simulated by the models. The small, high-resolution model domains were highly reliant on correct open boundary conditions to drive these larger-scale poleward flows. Multiply-nested models were no more effective than well-initialized local models in this respect.

Seasonal variability of the Canary Current: A numerical study

NASA Astrophysics Data System (ADS)

Mason, Evan; Colas, Francois; Molemaker, Jeroen; Shchepetkin, Alexander F.; Troupin, Charles; McWilliams, James C.; Sangrã, Pablo

2011-06-01

A high-resolution numerical model study of the Canary Basin in the northeast subtropical Atlantic Ocean is presented. A long-term climatological solution from the Regional Oceanic Modeling System (ROMS) reveals mesoscale variability associated with the Azores and Canary Current systems, the northwest African coastal upwelling, and the Canary Island archipelago. The primary result concerns the Canary Current (CanC) which, in the solution, transports ˜3 Sv southward in line with observations. The simulated CanC has a well-defined path with pronounced seasonal variability. This variability is shown to be mediated by the westward passage of two large annually excited counterrotating anomalous structures that originate at the African coast. The anomalies have a sea surface expression, permitting their validation using altimetry and travel at the phase speed of baroclinic planetary (Rossby) waves. The role of nearshore wind stress curl variability as a generating mechanism for the anomalies is confirmed through a sensitivity experiment forced by low-resolution winds. The resulting circulation is weak in comparison to the base run, but the propagating anomalies are still discernible, so we cannot discount a further role in their generation being played by annual reversals of the large-scale boundary flow that are known to occur along the African margin. An additional sensitivity experiment, where the Azores Current is removed by closing the Strait of Gibraltar presents the same anomalies and CanC behavior as the base run, suggesting that the CanC is rather insensitive to upstream variability from the Azores Current.

Physical connectivity between Pulley Ridge and Dry Tortugas coral reefs under the influence of the Loop Current/Florida Current system

NASA Astrophysics Data System (ADS)

Kourafalou, V. H.; Androulidakis, Y. S.; Kang, H.; Smith, R. H.; Valle-Levinson, A.

2018-07-01

The Pulley Ridge and Dry Tortugas coral reefs are among the most pristine, but also fragile, marine ecosystems of the continental United States. Understanding connectivity processes between them and with surrounding shelf and deep areas is fundamental for their management. This study focuses on the physical processes related to the connectivity of these reefs. Unprecedented in situ time series were used at these specific reef locations, together with satellite observations and numerical simulations, to investigate the dynamics controlling local circulation on the Southwestern Florida Shelf (SWFS) under oceanic influence. The approach of the Loop Current and Florida Current (LC/FC) system to the SWFS slope can induce 0.5 to 1 m/s offshore flows impacting the Pulley Ridge and Dry Tortugas reefs. On the other hand, when the LC/FC system retreats from the slope, onshore flows can carry open-sea waters over the coral reefs. Local formation of cyclonic eddies is possible near the Dry Tortugas reefs in the LC approach case and passage of upstream LC Frontal Eddies is possible in the LC retreat case. Offshore currents ∼1 m/s over the SWFS slope were also found during periods of anticyclonic LC Eddy separation. A novel finding is the shedding and northward propagation of mesoscale anticyclonic eddies from the core of the LC along the West Florida Shelf. Eddy shedding may have a broader effect on the dynamics of the shelf around the study reef areas. Long periods of LC/FC domination over these coral reefs (reaching several weeks to months) are characterized by strong (∼1 m/s) along-shelf currents and continuous upwelling processes, which may weaken the slope stratification and bring colder, deeper waters over the shelf-break and toward the shallower shelf region.

A Simple Criterion to Estimate Performance of Pulse Jet Mixed Vessels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pease, Leonard F.; Bamberger, Judith A.; Mahoney, Lenna A.

Pulse jet mixed process vessels comprise a key element of the U.S. Department of Energy’s strategy to process millions of gallons of legacy nuclear waste slurries. Slurry suctioned into a pulse jet mixer (PJM) tube at the end of one pulse is pneumatically driven from the PJM toward the bottom of the vessel at the beginning of the next pulse, forming a jet. The jet front traverses the distance from nozzle outlet to the bottom of the vessel and spreads out radially. Varying numbers of PJMs are typically arranged in a ring configuration within the vessel at a selected radiusmore » and operated concurrently. Centrally directed radial flows from neighboring jets collide to create a central upwell that elevates the solids in the center of the vessel when the PJM tubes expel their contents. An essential goal of PJM operation is to elevate solids to the liquid surface to minimize stratification. Solids stratification may adversely affect throughput of the waste processing plant. Unacceptably high slurry densities at the base of the vessel may plug the pipeline through which the slurry exits the vessel. Additionally, chemical reactions required for processing may not achieve complete conversion. To avoid these conditions, a means of predicting the elevation to which the solids rise in the central upwell that can be used during vessel design remains essential. In this paper we present a simple criterion to evaluate the extent of solids elevation achieved by a turbulent upwell jet. The criterion asserts that at any location in the central upwell the local velocity must be in excess of a cutoff velocity to remain turbulent. We find that local velocities in excess of 0.6 m/s are necessary for turbulent jet flow through both Newtonian and yield stress slurries. By coupling this criterion with the free jet velocity equation relating the local velocity to elevation in the central upwell, we estimate the elevation at which turbulence fails, and consequently the elevation at which the upwell fails to further lift the slurry. Comparing this elevation to the vessel fill level predicts whether the jet flow will achieve the full vertical extent of the vessel at the center. This simple local-velocity criterion determines a minimum PJM nozzle velocity at which the full vertical extent of the central upwell in PJM vessels will be turbulent. The criterion determines a minimum because flow in regions peripheral to the central upwelling jet may not be turbulent, even when the center of the vessel in the upwell is turbulent, if the jet pulse duration is too short. The local-velocity criterion ensures only that there is sufficient wherewithal for the turbulent jet flow to drive solids to the surface in the center of the vessel in the central upwell.« less

Instrumentation for optical ocean remote sensing

NASA Technical Reports Server (NTRS)

Esaias, W. E.

1991-01-01

Instruments used in ocean color remote sensing algorithm development, validation, and data acquisition which have the potential for further commercial development and marketing are discussed. The Ocean Data Acquisition System (ODAS) is an aircraft-borne radiometer system suitable for light aircraft, which has applications for rapid measurement of chlorophyll pigment concentrations along the flight line. The instrument package includes a three channel radiometer system for upwelling radiance, an infrared temperature sensor, a three-channel downwelling irradiance sensor, and Loran-C navigation. Data are stored on a PC and processed to transects or interpolated 'images' on the ground. The instrument has been in operational use for two and one half years. The accuracy of pigment concentrations from the instrument is quite good, even in complex Chesapeake Bay waters. To help meet the requirement for validation of future satellite missions, a prototype air-deployable drifting buoy for measurement of near-surface upwelled radiance in multiple channnels is undergoing test deployment. The optical drifter burst samples radiance, stores and processes the data, and uses the Argos system as a data link. Studies are underway to explore the limits to useful lifetime with respect to power and fouling.

Quantifying the impact of an upwelling filament on the physical-chemical-biological interactions off SW Iberia

NASA Astrophysics Data System (ADS)

Cravo, A.; Sanchez, R.; Monteiro, C.; Cardeira, S.; Madureira, M.; Rita, F.; Relvas, P.

2017-12-01

Upwelling filaments are mesoscale structures of cold water that stretch seaward in a tongue-like shape with origin in the coastal upwelling zone. Filaments off the Iberian Peninsula are recurrent, showing similarities with those in the Californian coast. The Cape São Vicente, the SW tip of the Iberian Peninsula, is the root of recurrent filaments observed in the satellite imagery during the upwelling season. However, the understanding of its physical and chemical impact on the biological productivity is rather limited. There, a relatively small filament ( 80 km long) was investigated through remote sensing and in situ multidisciplinary observations during an upwelling favourable wind relaxation event, but just after an intense upwelling period. A total of 42 CTD+Rosette casts up to 400 m depth were distributed on an almost regular grid of 15 km mean spacing guided by guided by satellite SST imagery transmitted to the ship in near-real time. The parameters sampled during the sea campaign included: velocity field sampled along the ship track through a hull-mounted 38 kHz RDI ADCP, meteorological variables, temperature, salinity, chlorophyll a, dissolved oxygen, nitrate, phosphate, silicate, cadmium, lead and zinc. The extent of the impact of the filament was evaluated by quantifying the cross-shelf transports of several properties. The amounts conveyed by the filament were much stronger than those expected by the wind-driven Ekman mechanism, showing that it represents an efficient feature for the exchange of water, dissolved and particulate matter from the productive shelf towards the oligotrophic offshore region. Considering the periods of strong upwelling events and the extent of their duration along the year, the amounts of exported matter will certainly enhance the biological productivity of these waters, including its fisheries. These filament data contribute to better understand the physical-chemical-biological interactions of this regional ecosystem.

Potential Improvements to Remote Primary Productivity Estimation in the Southern California Current System

NASA Astrophysics Data System (ADS)

Jacox, M.; Edwards, C. A.; Kahru, M.; Rudnick, D. L.; Kudela, R. M.

2012-12-01

A 26-year record of depth integrated primary productivity (PP) in the Southern California Current System (SCCS) is analyzed with the goal of improving satellite net primary productivity (PP) estimates. The ratio of integrated primary productivity to surface chlorophyll correlates strongly to surface chlorophyll concentration (chl0). However, chl0 does not correlate to chlorophyll-specific productivity, and appears to be a proxy for vertical phytoplankton distribution rather than phytoplankton physiology. Modest improvements in PP model performance are achieved by tuning existing algorithms for the SCCS, particularly by empirical parameterization of photosynthetic efficiency in the Vertically Generalized Production Model. Much larger improvements are enabled by improving accuracy of subsurface chlorophyll and light profiles. In a simple vertically resolved production model, substitution of in situ surface data for remote sensing estimates offers only marginal improvements in model r2 and total log10 root mean squared difference, while inclusion of in situ chlorophyll and light profiles improves these metrics significantly. Autonomous underwater gliders, capable of measuring subsurface fluorescence on long-term, long-range deployments, significantly improve PP model fidelity in the SCCS. We suggest their use (and that of other autonomous profilers such as Argo floats) in conjunction with satellites as a way forward for improved PP estimation in coastal upwelling systems.

How well-connected is the surface of the global ocean?

PubMed

Froyland, Gary; Stuart, Robyn M; van Sebille, Erik

2014-09-01

The Ekman dynamics of the ocean surface circulation is known to contain attracting regions such as the great oceanic gyres and the associated garbage patches. Less well-known are the extents of the basins of attractions of these regions and how strongly attracting they are. Understanding the shape and extent of the basins of attraction sheds light on the question of the strength of connectivity of different regions of the ocean, which helps in understanding the flow of buoyant material like plastic litter. Using short flow time trajectory data from a global ocean model, we create a Markov chain model of the surface ocean dynamics. The surface ocean is not a conservative dynamical system as water in the ocean follows three-dimensional pathways, with upwelling and downwelling in certain regions. Using our Markov chain model, we easily compute net surface upwelling and downwelling, and verify that it matches observed patterns of upwelling and downwelling in the real ocean. We analyze the Markov chain to determine multiple attracting regions. Finally, using an eigenvector approach, we (i) identify the five major ocean garbage patches, (ii) partition the ocean into basins of attraction for each of the garbage patches, and (iii) partition the ocean into regions that demonstrate transient dynamics modulo the attracting garbage patches.

Parga Chasma: Coronae and Rifting on Venus

NASA Technical Reports Server (NTRS)

Smrekar, S. E.; Stofan, E. R.; Buck, W. R.; Martin, P.

2005-01-01

The majority of coronae (quasicircular volcano-tectonic features) are found along rifts or fracture belts, and the majority of rifts have coronae [e.g. 1,2]. However, the relationship between coronae and rifts remains unclear [3-6]. There is evidence that coronae can form before, after, or synchronously with rifts [3,4]. The extensional fractures in the rift zones have been proposed to be a result of broad scale upwelling and traction on the lower lithosphere [7]. However, not all rift systems have a significant positive geoid anomaly, as would be expected for an upwelling site [8]. This could be explained if the rifts lacking anomalies are no longer active. Coronae are generally accepted to be sites of local upwelling [e.g. 1], but the observed rifting is frequently not radial to the coronae and extends well beyond the coronae into the surrounding plains. Thus the question remains as to whether the rifts represent regional extension, perhaps driven by mantle tractions, or if the coronae themselves create local thinning and extension of the lithosphere. In the first case, a regional extension model should be consistent with the observed characteristics of the rifts. In the latter case, a model of lithospheric loading and fracturing would be more appropriate. A good analogy may be the propagation of oceanic intraplate volcanoes [9].

Evaluation of upwelling infrared radiance from earth's atmosphere

NASA Technical Reports Server (NTRS)

Gupta, S. K.; Tiwari, S. N.

1975-01-01

Basic equations for calculating the upwelling atmospheric radiation are presented which account for various sources of radiation coming out at the top of the atmosphere. The theoretical formulation of the transmittance models (line-by-line and quasi-random band model) and the computational procedures used for the evaluation of the transmittance and radiance are discussed in detail. By employing the Lorentz line-by-line and quasi-random computer programs, model calculations were made to determine the upwelling radiance and signal change in the wave number interval of CO fundamental band. These results are useful in determining the effects of different interfering molecules, water vapor profiles, ground temperatures, and ground emittances on the upwelling radiance and signal change. This information is of vital importance in establishing the feasibility of measuring the concentrations of pollutants in the atmosphere from a gas filter correlation instrument flown on an aircraft or mounted on a satellite.

Lagrangian Timescales of Southern Ocean Upwelling in a Hierarchy of Model Resolutions

NASA Astrophysics Data System (ADS)

Drake, Henri F.; Morrison, Adele K.; Griffies, Stephen M.; Sarmiento, Jorge L.; Weijer, Wilbert; Gray, Alison R.

2018-01-01

In this paper we study upwelling pathways and timescales of Circumpolar Deep Water (CDW) in a hierarchy of models using a Lagrangian particle tracking method. Lagrangian timescales of CDW upwelling decrease from 87 years to 31 years to 17 years as the ocean resolution is refined from 1° to 0.25° to 0.1°. We attribute some of the differences in timescale to the strength of the eddy fields, as demonstrated by temporally degrading high-resolution model velocity fields. Consistent with the timescale dependence, we find that an average Lagrangian particle completes 3.2 circumpolar loops in the 1° model in comparison to 0.9 loops in the 0.1° model. These differences suggest that advective timescales and thus interbasin merging of upwelling CDW may be overestimated by coarse-resolution models, potentially affecting the skill of centennial scale climate change projections.

Yearly variation of bacterial production in the Arraial do Cabo protection area (Cabo Frio upwelling region): An evidence of anthropogenic pressure

PubMed Central

Coelho-Souza, Sérgio A.; Pereira, Gilberto C.; Coutinho, Ricardo; Guimarães, Jean R.D.

2013-01-01

Arraial do Cabo is where upwelling occurs more intensively on the Brazilian coast. Although it is a protection area it suffers anthropogenic pressure such as harbor activities and sporadic sewage emissions. Short-time studies showed a high variability of bacterial production (BP) in this region but none of them evaluated BP during long periods in a large spatial scale including stations under different natural (upwelling and cold fronts) and anthropogenic pressures. During 2006, we sampled surface waters 10 times (5 in upwelling and 5 in subsidence periods) in 8 stations and we measured BP, temperature as well as the concentrations of inorganic nutrients, pigments and particulate organic matter (POM). BP was up to 400 times higher when sewage emissions were observed visually and it had a positive correlation with ammonia concentrations. Therefore, in 2007, we did two samples (each during upwelling and subsidence periods) during sewage emissions in five stations under different anthropogenic pressure and we also measured particles abundance by flow cytometry. The 12 samples in the most impacted area confirmed that BP was highest when ammonia was higher than 2 μM, also reporting the highest concentrations of chlorophyll a and suspended particles. However, considering all measured variables, upwelling was the main disturbing factor but the pressure of fronts should not be neglected since it had consequences in the auto-heterotrophic coupling, increasing the concentrations of non fluorescent particles and POM. Stations clustered in function of natural and anthropogenic pressures degrees and both determined the temporal-spatial variability. PMID:24688533

Yearly variation of bacterial production in the Arraial do Cabo protection area (Cabo Frio upwelling region): an evidence of anthropogenic pressure.

PubMed

Coelho-Souza, Sérgio A; Pereira, Gilberto C; Coutinho, Ricardo; Guimarães, Jean R D

2013-12-01

Arraial do Cabo is where upwelling occurs more intensively on the Brazilian coast. Although it is a protection area it suffers anthropogenic pressure such as harbor activities and sporadic sewage emissions. Short-time studies showed a high variability of bacterial production (BP) in this region but none of them evaluated BP during long periods in a large spatial scale including stations under different natural (upwelling and cold fronts) and anthropogenic pressures. During 2006, we sampled surface waters 10 times (5 in upwelling and 5 in subsidence periods) in 8 stations and we measured BP, temperature as well as the concentrations of inorganic nutrients, pigments and particulate organic matter (POM). BP was up to 400 times higher when sewage emissions were observed visually and it had a positive correlation with ammonia concentrations. Therefore, in 2007, we did two samples (each during upwelling and subsidence periods) during sewage emissions in five stations under different anthropogenic pressure and we also measured particles abundance by flow cytometry. The 12 samples in the most impacted area confirmed that BP was highest when ammonia was higher than 2 μM, also reporting the highest concentrations of chlorophyll a and suspended particles. However, considering all measured variables, upwelling was the main disturbing factor but the pressure of fronts should not be neglected since it had consequences in the auto-heterotrophic coupling, increasing the concentrations of non fluorescent particles and POM. Stations clustered in function of natural and anthropogenic pressures degrees and both determined the temporal-spatial variability.

Transport of terrigenous polycyclic aromatic hydrocarbons affected by the coastal upwelling in the northwestern coast of South China Sea.

PubMed

Ya, Miaolei; Wu, Yuling; Li, Yongyu; Wang, Xinhong

2017-10-01

Coastal upwelling prevails in the coast of Hainan Island, the northern South China Sea (SCS) during summer. We studied the influences of the upwelling on the horizontal and vertical transport of terrigenous polycyclic aromatic hydrocarbons (PAHs). PAHs in dissolved and suspended particulate phase of water samples were determined in the upper (depth < 1 m) and water column (depth > 10 m). PAH levels decreased sharply from inshore to offshore to open sea. The results showed that terrestrial input was the main source of coastal PAHs. Perylene, an important indicator of land plant-derived PAH, showed the significant correlation with PAHs (p < 0.005). This implied that fluvial transport was the primary pathway of terrigenous PAHs into the coast of northern SCS. Variations of the concentrations, compositions and diagnostic ratios of PAHs, accompanied the partition equilibrium in the water column, could indicate the selective degradation of PAHs by the plankton affected by upwelling. Different from the "traditional" transport pathway of PAHs in the water column (surface enrichment-depth depletion distribution), the upwelling could provide the original driver to elevate the upward diffusion of sediment entrained contaminants towards the intermediate even the upper waters. It could also enhance the outward diffusion of terrigenous PAHs accompanied by the offshore transport of the upper waters. Therefore, the transport pathway of PAHs can be summarized by the coastal upwelling rising PAHs with their subsequent transport offshore and settling in the adjacent open sea. Copyright © 2017 Elsevier Ltd. All rights reserved.

Environmental Controls of Shellfish-Toxigenic Vibrio Bacteria in Oregon's Coasts and Estuaries

NASA Astrophysics Data System (ADS)

Gradoville, M. R.; Häse, C.; White, A. E.

2016-02-01

Vibrio species are a known and persistent concern for economically important aquaculture efforts. In Pacific Northwest shellfish hatcheries, vibriosis, caused by toxigenic Vibrio, has been responsible for major mortality events in recent decades — events that are often irregular and unpredictable. The success of shellfish hatcheries is critically linked to the chemical and biological composition of their seawater resources; thus, it is pertinent to understand the biogeochemical drivers of toxigenic Vibrio in their planktonic state. Recent evidence suggests that vibriosis outbreaks in Netarts Bay, Oregon may be related to wind-driven coastal upwelling, either through the advection of toxigenic Vibrio residing in upwelling source water, or through the creation of favorable growth conditions within the estuary. Here, we present data tracking shellfish-toxigenic Vibrio bacteria in Oregon estuaries and coastal waters through the 2015 upwelling season. Estuarine samples were collected from Netarts Bay and Yaquina Bay in May-October 2015 over a range of upwelling intensities, tidal heights, and biogeochemical conditions. Additionally, samples were collected at multiple depths from offshore coastal Oregon stations in order to test the hypothesis that toxigenic Vibrio reside in upwelling source waters. PCR-based methods were used to quantify the known shellfish pathogen V. coralliilyticus in estuary and seawater samples. These toxigenic Vibrio abundances were correlated to local environmental conditions, including temperature, salinity, carbonate chemistry, nutrients, and chlorophyll a concentrations, as well as coastal wind stress and upwelling intensity. Our analysis aims to define the environmental controls of toxigenic Vibrio in their free-living oceanic state, information that can be used to prevent future disease outbreaks in local shellfish hatcheries.

Oceanographic upwelling conditions influence signaling pathways involved in muscle growth of intertidal fish.

PubMed

Zuloaga, Rodrigo; Almarza, Oscar; Valdés, Juan A; Molina, Alfredo; Pulgar, José

2018-04-01

Few studies have addressed the impact of the upwelling oceanographical conditions on biological processes, such as growth, using a molecular and physiological approach. Upwelling conditions are characterized by low temperature seawater and high nutrient availability, which represents an ideal opportunity to understand how habitat modulates animal performance at different levels of biological complexity. We aimed to assess intraspecific variations in weight, oxygen consumption, protein content, and key signaling pathways involved in muscle-growth (protein kinase B (AKT) and extracellular signal-regulated kinase (ERK)) under experimental trials considering high/low seawater temperatures with full/restricted food rations. For this purpose, we studied Girella laevifrons, one of the most abundant fish species inhabiting rocky intertidal zones along the Eastern South Pacific coasts. Using fish obtained from upwelling (U) and non-upwelling (NU) zones, we reported that U animals displayed higher growth performance during both contrasting trials, with a weight gain (~3 g), lower oxygen consumption (~12%), and higher protein contents (~20%). Only ERK showed significant differences during the trials (~2-fold downregulation between NU and U fish). We also found that U fish increased protein ubiquitination in high water temperature and restricted food ration in contrast to NU fish. Our results help to elucidate how upwelling conditions may influence fish growth at physiological and molecular levels. Still, future analyses are necessary to improve the information regarding the impact of U and NU condition on animals, as well as the possible applications of this data in the aquaculture industry. Copyright © 2018 Elsevier Inc. All rights reserved.

The Origin and Mantle Dynamics of Quaternary Intraplate Volcanism in Northeast China From Joint Inversion of Surface Wave and Body Wave

NASA Astrophysics Data System (ADS)

Guo, Zhen; Wang, Kai; Yang, Yingjie; Tang, Youcai; John Chen, Y.; Hung, Shu-Huei

2018-03-01

We present a 3-D model of NE China by joint inversion of body and surface waves. The joint inversion significantly improves the resolution at shallow depths compared with body wave tomography alone and provides seismic evidence for the origin of Quaternary volcanism in NE China. Our model reveals that the mantle upwelling beneath the Changbaishan volcano originates from the transition zone and extends up to 60 km, and spreads at the base of the lithosphere with the upwelling head 5 times wider than the raising tail in the lower upper mantle. However, low velocities beneath the Halaha and Abaga volcanoes in the Xingmeng belt are confined to depths shallower than 150 km, suggesting that magmatism in the Xingmeng belt is more likely caused by localized asthenospheric upwelling at shallow depths rather than from the common deep source. A small-scale sublithospheric mantle convection may control the spatial and temporal distribution of Quaternary magmatism in NE China; that is, the upwelling beneath the Changbaishan volcano triggers the downwelling beneath the southern Songliao basin, where the high velocity imaged extends to 300 km. The downwelling may further induce localized upwelling in the surrounding areas, such as the Halaha and Abaga volcanoes. Thanks to the joint constraints from both surface and body waves, we can estimate the dimension of the convection cell. The convection cell is located between 42°N and 45°N, spreads around 500 km in the W-E direction measured from the distance between centers of downwelling and upwelling, and extends to 300 km vertically.

Surface radiation budget for climate applications

NASA Technical Reports Server (NTRS)

Suttles, J. T. (Editor); Ohring, G. (Editor)

1986-01-01

The Surface Radiation Budget (SRB) consists of the upwelling and downwelling radiation fluxes at the surface, separately determined for the broadband shortwave (SW) (0 to 5 micron) and longwave (LW) (greater than 5 microns) spectral regions plus certain key parameters that control these fluxes, specifically, SW albedo, LW emissivity, and surface temperature. The uses and requirements for SRB data, critical assessment of current capabilities for producing these data, and directions for future research are presented.

Chromophoric and fluorescent dissolved organic matter in and above the oxygen minimum zone off Peru

NASA Astrophysics Data System (ADS)

Loginova, A. N.; Thomsen, S.; Engel, A.

2016-11-01

As a result of nutrient upwelling, the Peruvian coastal system is one of the most productive regions in the ocean. Sluggish ventilation of intermediate waters, characteristic for the Eastern Tropical South Pacific (ETSP) and microbial degradation of a high organic matter load promotes deoxygenation at depth. Dissolved organic matter (DOM) plays a key role in microbial respiration and carbon cycling, but little is known on DOM distribution and cycling in the ETSP. DOM optical properties give important insights on DOM sources, structure and biogeochemical reactivity. Here, we present data and a conceptual view on distribution and cycling of chromophoric (CDOM) and fluorescent (FDOM) DOM in and above the oxygen minimum zone (OMZ) off Peru. Five fluorescent components were identified during PARAFAC analysis. Highest intensities of CDOM and of the amino acid-like fluorescent component (C3) occurred above the OMZ and coincided with maximum chl a concentrations, suggesting phytoplankton productivity as major source. High intensities of a marine humic-like fluorescent component (C1), observed in subsurface waters, indicated in situ microbial reworking of DOM. FDOM release from inner shelf sediment was determined by seawater analysis and continuous glider sensor measurement and included a humic-like component (C2) with a signature typical for terrestrially derived humic acids. Upwelling supplied humic-like substances to the euphotic zone. Photo-reactions were likely involved in the production of a humic-like fluorescent component (C5). Our data show that variable biological and physical processes need to be considered for understanding DOM cycling in a highly dynamic coastal upwelling system like the ETSP off Peru.

Development of Embryonic Market Squid, Doryteuthis opalescens, under Chronic Exposure to Low Environmental pH and [O2].

PubMed

Navarro, Michael O; Kwan, Garfield T; Batalov, Olga; Choi, Chelsea Y; Pierce, N Tessa; Levin, Lisa A

2016-01-01

The market squid, Doryteuthis opalescens, is an important forage species for the inshore ecosystems of the California Current System. Due to increased upwelling and expansion of the oxygen minimum zone in the California Current Ecosystem, the inshore environment is expected to experience lower pH and [O2] conditions in the future, potentially impacting the development of seafloor-attached encapsulated embryos. To understand the consequences of this co-occurring environmental pH and [O2] stress for D. opalescens encapsulated embryos, we performed two laboratory experiments. In Experiment 1, embryo capsules were chronically exposed to a treatment of higher (normal) pH (7.93) and [O2] (242 μM) or a treatment of low pH (7.57) and [O2] (80 μM), characteristic of upwelling events and/or La Niña conditions. The low pH and low [O2] treatment extended embryo development duration by 5-7 days; embryos remained at less developed stages more often and had 54.7% smaller statolith area at a given embryo size. Importantly, the embryos that did develop to mature embryonic stages grew to sizes that were similar (non-distinct) to those exposed to the high pH and high [O2] treatment. In Experiment 2, we exposed encapsulated embryos to a single stressor, low pH (7.56) or low [O2] (85 μM), to understand the importance of environmental pH and [O2] rising and falling together for squid embryogenesis. Embryos in the low pH only treatment had smaller yolk reserves and bigger statoliths compared to those in low [O2] only treatment. These results suggest that D. opalescens developmental duration and statolith size are impacted by exposure to environmental [O2] and pH (pCO2) and provide insight into embryo resilience to these effects.

Risks of ocean acidification in the California Current food web and fisheries: ecosystem model projections.

PubMed

Marshall, Kristin N; Kaplan, Isaac C; Hodgson, Emma E; Hermann, Albert; Busch, D Shallin; McElhany, Paul; Essington, Timothy E; Harvey, Chris J; Fulton, Elizabeth A

2017-04-01

The benefits and ecosystem services that humans derive from the oceans are threatened by numerous global change stressors, one of which is ocean acidification. Here, we describe the effects of ocean acidification on an upwelling system that already experiences inherently low pH conditions, the California Current. We used an end-to-end ecosystem model (Atlantis), forced by downscaled global climate models and informed by a meta-analysis of the pH sensitivities of local taxa, to investigate the direct and indirect effects of future pH on biomass and fisheries revenues. Our model projects a 0.2-unit drop in pH during the summer upwelling season from 2013 to 2063, which results in wide-ranging magnitudes of effects across guilds and functional groups. The most dramatic direct effects of future pH may be expected on epibenthic invertebrates (crabs, shrimps, benthic grazers, benthic detritivores, bivalves), and strong indirect effects expected on some demersal fish, sharks, and epibenthic invertebrates (Dungeness crab) because they consume species known to be sensitive to changing pH. The model's pelagic community, including marine mammals and seabirds, was much less influenced by future pH. Some functional groups were less affected to changing pH in the model than might be expected from experimental studies in the empirical literature due to high population productivity (e.g., copepods, pteropods). Model results suggest strong effects of reduced pH on nearshore state-managed invertebrate fisheries, but modest effects on the groundfish fishery because individual groundfish species exhibited diverse responses to changing pH. Our results provide a set of projections that generally support and build upon previous findings and set the stage for hypotheses to guide future modeling and experimental analysis on the effects of OA on marine ecosystems and fisheries. © 2017 John Wiley & Sons Ltd.

Development of Embryonic Market Squid, Doryteuthis opalescens, under Chronic Exposure to Low Environmental pH and [O2

PubMed Central

Navarro, Michael O.; Kwan, Garfield T.; Batalov, Olga; Choi, Chelsea Y.; Pierce, N. Tessa; Levin, Lisa A.

2016-01-01

The market squid, Doryteuthis opalescens, is an important forage species for the inshore ecosystems of the California Current System. Due to increased upwelling and expansion of the oxygen minimum zone in the California Current Ecosystem, the inshore environment is expected to experience lower pH and [O2] conditions in the future, potentially impacting the development of seafloor-attached encapsulated embryos. To understand the consequences of this co-occurring environmental pH and [O2] stress for D. opalescens encapsulated embryos, we performed two laboratory experiments. In Experiment 1, embryo capsules were chronically exposed to a treatment of higher (normal) pH (7.93) and [O2] (242 μM) or a treatment of low pH (7.57) and [O2] (80 μM), characteristic of upwelling events and/or La Niña conditions. The low pH and low [O2] treatment extended embryo development duration by 5–7 days; embryos remained at less developed stages more often and had 54.7% smaller statolith area at a given embryo size. Importantly, the embryos that did develop to mature embryonic stages grew to sizes that were similar (non-distinct) to those exposed to the high pH and high [O2] treatment. In Experiment 2, we exposed encapsulated embryos to a single stressor, low pH (7.56) or low [O2] (85 μM), to understand the importance of environmental pH and [O2] rising and falling together for squid embryogenesis. Embryos in the low pH only treatment had smaller yolk reserves and bigger statoliths compared to those in low [O2] only treatment. These results suggest that D. opalescens developmental duration and statolith size are impacted by exposure to environmental [O2] and pH (pCO2) and provide insight into embryo resilience to these effects. PMID:27936085

Effects of Climate Change on Sardine Productivity in the California Current System

NASA Astrophysics Data System (ADS)

Baumgartner, T. R.; Auad, G.; Miller, A. J.

2007-05-01

The Pacific sardine (Sardinops sagax caeruleus) is one of several coastal pelagic, planktivorous species of fish that provide important trophic links within the ecosystems of the major eastern and western boundary currents. Significant and persistent change in sardine productivity has occurred in the California Current over interdecadal periods in response to reorganization of basin-wide, ocean-atmosphere circulation. Less extreme, but still significant changes in sardine productivity are associated with interannual to decadal-scale climate variability. A precipitous decline of the sardine population began in the mid-1940s with a shift in climate leading to cooling of the California Current system. While the decline, and ultimately the collapse of the population, was exacerbated by intensive fishing, the sardine also suffered a severe reduction in productivity with the southward contraction of favorable thermal habitat that led to restriction of the population to the waters off Southern California and Baja California. This southward displacement resulted in geographic separation of the population from the region off central and northern California that is characterized by significantly higher concentrations of zooplankton that supported the previous levels of success in spawning and larval development. The climate shift in 1976-77 led to the recovery of the population and extension of its range of distribution northwards into the waters off British Columbia. The relation of reproductive success of the sardine population to interannual and decadal climate change was examined for the period 1982-2005 using a suite of seasonal indices representing climate processes and habitat conditions (including zooplankton food levels) occurring through the different stages in the sardine life cycle. We used both stepwise regression and EOF analyses to determine the association between levels of recruitment success and seasonal indices of the Pacific Decadal Oscillation, Ekman pumping (measured at 35°N, 122.5°W), coastal upwelling (at 36°N, 122°W) and zooplankton biomass (represented by values from the center of sardine spawning). The seasonal indices of the PDO are positively correlated with reproductive success, while an inverse relationship between the PDO indices and coastal upwelling is consistent with reduced equatorward flow during coastal warming that favors sardine reproduction. Results also show an unambiguous inverse relationship between Ekman pumping and sardine recruitment success indicating the negative influence of increased offshore transport on the survival of eggs and larvae. There is a surprising lack of association between recruitment success and zooplankton biomass, interpreted to mean that food was not limiting for sardine reproduction during the period analyzed (in the warm regime after 1977). Based on the results of this study, we anticipate that global warming will favor the maintenance of the sardine population over its present range from the Gulf of California into the waters of British Columbia throughout the current century.

Seasonal and Vegetational Variation in Albedo Measured During CERES Ground-Validation Pilot Study

NASA Technical Reports Server (NTRS)

Schuster, G. L.; Whitlock, C. H.; Plant, J. V.; Wheeler, R. J.; Moats, C. D.; Larman, K. T.; Ayers, J. K.; Feldl, E. K.

1997-01-01

The Clouds and the Earth's Radiant Energy System (CERES) satellite is scheduled for launch in the Fall of 1997 aboard the Tropical Rainfall Measuring Mission (TRMM). A surface measurement pilot study has been initiated in a 37-km region near Richmond, VA, for comparison with the CERES surface flux retrievals. Two-minute averaged upwelling and downwelling surface fluxes over a mostly deciduous forest have been recorded daily for the past two years, and show a broadband, shortwave daily albedo increase during the summer months. Evidence is presented that indicates vegetational changes in the forest as the overriding mechanism for this change. Upwelling flux measured over the entire region by helicopter-mounted instrumentation has been processed for four solar seasons. Future plans include the installation of four more albedo surface sites over various types of vegetation throughout the region.

Back to the future: using historical climate variation to project near-term shifts in habitat suitable for coast redwood.

PubMed

Fernández, Miguel; Hamilton, Healy H; Kueppers, Lara M

2015-11-01

Studies that model the effect of climate change on terrestrial ecosystems often use climate projections from downscaled global climate models (GCMs). These simulations are generally too coarse to capture patterns of fine-scale climate variation, such as the sharp coastal energy and moisture gradients associated with wind-driven upwelling of cold water. Coastal upwelling may limit future increases in coastal temperatures, compromising GCMs' ability to provide realistic scenarios of future climate in these coastal ecosystems. Taking advantage of naturally occurring variability in the high-resolution historic climatic record, we developed multiple fine-scale scenarios of California climate that maintain coherent relationships between regional climate and coastal upwelling. We compared these scenarios against coarse resolution GCM projections at a regional scale to evaluate their temporal equivalency. We used these historically based scenarios to estimate potential suitable habitat for coast redwood (Sequoia sempervirens D. Don) under 'normal' combinations of temperature and precipitation, and under anomalous combinations representative of potential future climates. We found that a scenario of warmer temperature with historically normal precipitation is equivalent to climate projected by GCMs for California by 2020-2030 and that under these conditions, climatically suitable habitat for coast redwood significantly contracts at the southern end of its current range. Our results suggest that historical climate data provide a high-resolution alternative to downscaled GCM outputs for near-term ecological forecasts. This method may be particularly useful in other regions where local climate is strongly influenced by ocean-atmosphere dynamics that are not represented by coarse-scale GCMs. © 2015 John Wiley & Sons Ltd.

Land-atmosphere-ocean interactions in the southeastern Atlantic: interannual variability

NASA Astrophysics Data System (ADS)

Sun, Xiaoming; Vizy, Edward K.; Cook, Kerry H.

2018-02-01

Land-atmosphere-ocean interactions in the southeastern South Atlantic and their connections to interannual variability are examined using a regional climate model coupled with an intermediate-level ocean model. In austral summer, zonal displacements of the South Atlantic subtropical high (SASH) can induce variations of mixed-layer currents in the Benguela upwelling region through surface wind stress curl anomalies near the Namibian coast, and an eastward shifted SASH is related to the first Pacific-South American mode. When the SASH is meridionally displaced, mixed layer vertically-integrated Ekman transport anomalies are mainly a response to the change of alongshore surface wind stress. The latitudinal shift of the SASH tends to dampen the anomalous alongshore wind by modulating the land-sea thermal contrast, while opposed by oceanic diffusion. Although the position of the SASH is closely linked to the phase of El Niño-Southern Oscillation (ENSO) and the southern annular mode (SAM) in austral summer, an overall relationship between Benguela upwelling strength and ENSO or SAM is absent. During austral winter, variations of the mixed layer Ekman transport in the Benguela upwelling region are connected to the strength of the SASH through its impact on both coastal wind stress curl and alongshore surface wind stress. Compared with austral summer, low-level cloud cover change plays a more important role. Although wintertime sea surface temperature fluctuations in the equatorial Atlantic are strong and may act to influence variability over the northern Benguela area, the surface heat budget analysis suggests that local air-sea interactions dominate.

Diatom Evidence for Climatic Changes Associated With the Slowdown of the Meridional Overturning Circulation in the Last 50 Years in the Mexican Tropical Pacific.

NASA Astrophysics Data System (ADS)

Machain-Castillo, M. L.; Almaraz-Ruiz, L.; Esparza-Alvarez, M. A.; Ruiz-Fernandez, A. C.; Sanchez-Cabeza, J. A.; Hernandez-Becerril, D. U.

2016-12-01

Laminated sediments from the Gulf of Tehuantepec, Mexican Tropical Pacific, reveal climatic variability during the last 50 years. The Gulf of Tehuantepec is characterized by strong upwelling during the autumn-winter season due to intense northern winds. Upwelling supplies high nutrient concentrations and cold water to the ocean surface, resulting in high biological productivity, including diatom blooms. The rest of the year winds are relatively calm and currents predominantly flow to the Northeast. A box core collected in the area beneath the wind axes (750m water depth) showed sub-millimeter to millimeter scale laminated sediments. Laminae were separated and analyzed for diatoms. Chronology was obtained by 210Pb dating. Three diatom associations were recognized in the sediments studied: a cold water association dominated by Thalasionema nitzschioides, T. nitzchioides var. parva, Lioloma pacificum and Chaetoceros spores; an association dominated by Fragilariopsis doliolus, T. bacillare and Thalassiosira oestrupii, more characteristic of temperate waters, and an association of warm waters characterized by Neodelphineis pelagica, T. pseudonitzschioides, Actinocyclus ellipticus, Cyclotella litoralis and Thalassiosira decipiens. Abundance of diatoms is higher (up to 344 106 valves g-1) in the coldest association and lowest (83 106 valves g-1) in the warmer one. Although upwelling species are present throughout the core, we observed a decrease in diatom abundance and an increase in temperate and warm water taxa from the 1960's-1970's. This trend is coincident with the climatic changes produced by the slowdown of the meridional overturning circulation proposed for the past century and global warming.

Influence of El Niño and Indian Ocean Dipole on sea level variability in the Bay of Bengal

NASA Astrophysics Data System (ADS)

Sreenivas, P.; Gnanaseelan, C.; Prasad, K. V. S. R.

2012-01-01

Zonally oscillating seasonal equatorial winds generate pairs of upwelling and downwelling Kelvin waves in the Equatorial Indian Ocean, which then advance in to the coastal Bay of Bengal. The first (second) equatorial upwelling Kelvin wave has its origin in the western (eastern) basin, whereas the downwelling Kelvin waves originate in the central basin. The observed interannual variability of these Kelvin waves is highly governed by the associated zonal wind changes in the central and eastern equatorial Indian Ocean during the anomalous years. The second downwelling (upwelling) Kelvin wave is absent (weak) during El Niño (La Niña) years, whereas the second upwelling Kelvin wave strengthened during El Niño years both in the equatorial Indian Ocean and Bay of Bengal. The large scale off equatorial Rossby waves occasionally feedback the equatorial Kelvin waves, which then strengthen the Bay of Bengal coastal Kelvin waves. The coastal Kelvin waves and the associated radiated Rossby waves from east play a dominant role in the mesoscale eddy generation in Bay of Bengal. The analysis of cyclogenesis characteristics in the bay over the past 65 years revealed that the active (suppressed) phases of cyclogenesis are coinciding with the downwelling (upwelling) planetary waves which influence the cyclone heat potential by altering the thermocline depth.

The Influence of Hydrologic Conditions on the Distribution of Baleen Whales in the Antarctic (Raspredelenie Usatykh Kitov v Anarktike v Zabisimosti ot Gidrologicheskikh Uslovii),

DTIC Science & Technology

where a semistationary cyclonic system coincides with plankton rich waters upwelling from great depths. Whales locate these feeding grounds through...growth. They also travel parallel to isohalines to remain in the feeding grounds. (Author)

SIMULATING TEMPORAL VARIATIONS IN NUTRIENT, PHYTOPLANKTON, AND ZOOPLANKTON ON THE INNER OREGON SHELF

EPA Science Inventory

The objective of this study is to use a numerical model to examine the linkages between physical processes and temporal variability in the plankton dynamics in a coastal upwelling system. We used a nutrient-phytoplankton-zooplankton model coupled to a two-dimensional circulation...

Influence of Venus topography on the zonal wind and UV albedo at cloud top level: The role of stationary gravity waves

NASA Astrophysics Data System (ADS)

Bertaux, Jean-Loup; Khatuntsev, I. V.; Hauchecorne, A.; Markiewicz, W. J.; Marcq, E.; Lebonnois, S.; Patsaeva, M.; Turin, A.; Fedorova, A.

2016-06-01

Based on the analysis of UV images (at 365 nm) of Venus cloud top (altitude 67 ± 2 km) collected with Venus Monitoring Camera on board Venus Express (VEX), it is found that the zonal wind speed south of the equator (from 5°S to 15°S) shows a conspicuous variation (from -101 to -83 m/s) with geographic longitude of Venus, correlated with the underlying relief of Aphrodite Terra. We interpret this pattern as the result of stationary gravity waves produced at ground level by the uplift of air when the horizontal wind encounters a mountain slope. These waves can propagate up to the cloud top level, break there, and transfer their momentum to the zonal flow. Such upward propagation of gravity waves and influence on the wind speed vertical profile was shown to play an important role in the middle atmosphere of the Earth by Lindzen (1981) but is not reproduced in the current GCM of Venus atmosphere from LMD. (Laboratoire de Météorologie Dynamique) In the equatorial regions, the UV albedo at 365 nm varies also with longitude. We argue that this variation may be simply explained by the divergence of the horizontal wind field. In the longitude region (from 60° to -10°) where the horizontal wind speed is increasing in magnitude (stretch), it triggers air upwelling which brings the UV absorber at cloud top level and decreases the albedo and vice versa when the wind is decreasing in magnitude (compression). This picture is fully consistent with the classical view of Venus meridional circulation, with upwelling at equator revealed by horizontal air motions away from equator: the longitude effect is only an additional but important modulation of this effect. This interpretation is comforted by a recent map of cloud top H2O, showing that near the equator the lower UV albedo longitude region is correlated with increased H2O. We argue that H2O enhancement is the sign of upwelling, suggesting that the UV absorber is also brought to cloud top by upwelling.

Observed longitude variations of zonal wind, UV albedo and H2O at Venus cloud top level: the role of stationary gravity waves generated by Venus topography

NASA Astrophysics Data System (ADS)

Bertaux, Jean-Loup; Hauchecorne, Alain; khatuntsev, Igor; Markiewicz, Wojciech; Marcq, emmanuel; Lebonnois, Sebastien; Patsaeva, Marina; Turin, Alexander; Fedorova, Anna

2016-10-01

Based on the analysis of UV images (at 365 nm) of Venus cloud top (altitude 67±2 km) collected with VMC (Venus Monitoring Camera) on board Venus Express (VEX), it is found that the zonal wind speed south of the equator (from 5°S to 15°S) shows a conspicuous variation (from -101 to -83 m/s) with geographic longitude of Venus, correlated with the underlying relief of Aphrodite Terra. We interpret this pattern as the result of stationary gravity waves produced at ground level by the up lift of air when the horizontal wind encounters a mountain slope. These waves can propagate up to the cloud top level, break there and transfer their momentum to the zonal flow. Such upward propagation of gravity waves and influence on the wind speed vertical profile was shown to play an important role in the middle atmosphere of the Earth but is not reproduced in the current GCM of Venus atmosphere from LMD.In the equatorial regions, the UV albedo of clouds at 365 nm and the H2O mixing ratio at cloud top varies also with longitude, with an anti-correlation: the more H2O, the darker are the clouds. We argue that these variations may be simply explained by the divergence of the horizontal wind field. In the longitude region (from 60° to -10°) where the horizontal wind speed is increasing in magnitude (stretch), it triggers air upwelling which brings both the UV absorber and H2O at cloud top level and decreases the albedo, and vice-versa when the wind is decreasing in magnitude (compression). This picture is fully consistent with the classical view of Venus meridional circulation, with upwelling at equator revealed by horizontal air motions away from equator: the longitude effect is only an additional but important modulation of this effect. We argue that H2O enhancement is the sign of upwelling because the H2O mixing ratio decreases with altitude, comforting the view that the UV absorber is also brought to cloud top by upwelling.

A modeling study on the hydrodynamics of a coastal embayment occupied by mussel farms (Ria de Ares-Betanzos, NW Iberian Peninsula)

NASA Astrophysics Data System (ADS)

Duarte, Pedro; Alvarez-Salgado, Xosé Antón; Fernández-Reiriz, Maria José; Piedracoba, Silvia; Labarta, Uxío

2014-06-01

The present study suggests that both under upwelling and downwelling winds, the residual circulation of Ria de Ares-Betanzos remains positive with a strong influence from river discharge and a positive feedback from wind, unlike what is generally accepted for Galician rias. Furthermore, mussel cultivation areas may reduce residual velocities by almost 40%, suggesting their potential feedbacks on food replenishment for cultivated mussels. The Ria de Ares-Betanzos is a partially stratified estuary in the NW Iberian upwelling system where blue mussels are extensively cultured on hanging ropes. This type of culture depends to a large extent on water circulation and residence times, since mussels feed on suspended particles. Therefore, understanding the role of tides, continental runoff, and winds on the circulation of this embayment has important practical applications. Furthermore, previous works have emphasized the potential importance of aquaculture leases on water circulation within coastal ecosystems, with potential negative feedbacks on production carrying capacity. Here we implemented and validated a 3D hydrodynamic numerical model for the Ria de Ares-Betanzos to (i) evaluate the relative importance of the forcing agents on the circulation within the ria and (ii) estimate the importance of culture leases on circulation patterns at the scale of the mussel farms from model simulations. The model was successfully validated with empirical current velocity data collected during July and October 2007 using an assortment of efficiency criteria. Model simulations were carried out to isolate the effects of wind and river flows on circulation patterns.

The Angola Current and its seasonal variability as observed at 11°S

NASA Astrophysics Data System (ADS)

Kopte, Robert; Brandt, Peter; Dengler, Marcus; Claus, Martin; Greatbatch, Richard J.

2016-04-01

The eastern boundary circulation off the coast of Angola has been described only sparsely to date. The region off Angola, which connects the equatorial Atlantic and the Angola-Benguela upwelling regime, is of particular interest to understand the relative importance of transient equatorial versus local forcing of the observed variability in the coastal upwelling region. For the first time multi-year velocity observations of the Angola Current at 11°S are available. From July 2013 to November 2015 a bottom shield equipped with an ADCP had been deployed at 500m water depth, accompanied by a mooring sitting on the 1200m-isobath with an ADCP being installed at 500m depth. Both upward-looking instruments measured the current speed up to about 50m below the sea surface. During the deployment period the Angola Current was characterized by a weak southward mean flow of 5-8 cm/s at 50m depth (slightly stronger at the in-shore mooring position), with the southward current penetrating down to about 200m depth. The alongshore velocity component reveals a pronounced seasonal variability. It is dominated by 120-day, semi-annual, and annual oscillations with distinct baroclinic structures. Here we apply a reduced gravity model of the tropical Atlantic for the first five baroclinic modes forced with interannually varying wind stress to investigate the seasonal variability along the equatorial and coastal waveguides. In the equatorial Atlantic the 120-day, semi-annual, and annual oscillations are associated with resonant basin modes of the 1st, 2nd, and 4th baroclinic mode, respectively. These basin modes are composed of equatorial Kelvin and Rossby waves as well as coastally trapped waves. The reduced gravity model is further used to study the respective role of the remote equatorial forcing, more specifically the influence of equatorial basin modes via coastally trapped waves, and the local forcing for the observed seasonal variability and associated baroclinic structure of the Angola Current at 11°S.

Temporal characteristics of coherent flow structures generated over alluvial sand dunes, Mississippi River, revealed by acoustic doppler current profiling and multibeam echo sounding

USGS Publications Warehouse

Czuba, John A.; Oberg, Kevin A.; Best, Jim L.; Parsons, Daniel R.; Simmons, S. M.; Johnson, K.K.; Malzone, C.

2009-01-01

This paper investigates the flow in the lee of a large sand dune located at the confluence of the Mississippi and Missouri Rivers, USA. Stationary profiles collected from an anchored boat using an acoustic Doppler current profiler (ADCP) were georeferenced with data from a real-time kinematic differential global positioning system. A multibeam echo sounder was used to map the bathymetry of the confluence and provided a morphological context for the ADCP measurements. The flow in the lee of a low-angle dune shows good correspondence with current conceptual models of flow over dunes. As expected, quadrant 2 events (upwellings of low-momentum fluid) are associated with high backscatter intensity. Turbulent events generated in the lower lee of a dune near the bed are associated with periods of vortex shedding and wake flapping. Remnant coherent structures that advect over the lower lee of the dune in the upper portion of the water column, have mostly dissipated and contribute little to turbulence intensities. The turbulent events that occupy most of the water column in the upper lee of the dune are associated with periods of wake flapping.

Impact of Indian ocean dipole on the coastal upwelling features off the southwest coast of India

NASA Astrophysics Data System (ADS)

Nigam, Tanuja; Pant, Vimlesh; Prakash, Kumar Ravi

2018-05-01

A three-dimensional regional ocean model is used to examine the impact of positive Indian ocean dipole (pIOD) events on the coastal upwelling features at the southwest coast of India (SWCI). Two model experiments are carried out with different surface boundary conditions that prevailed in the normal and pIOD years from 1982 to 2010. Model experiments demonstrate the weakening of coastal upwelling at the SWCI in the pIOD years. The reduced southward meridional wind stress off the SWCI leads to comparatively lower offshore Ekman transport during August-October in the pIOD years to that in normal years. The suppressed coastal upwelling results in warmer sea surface temperature and deeper thermocline in the pIOD years during June-September. The offshore spatial extent of upwelled colder (< 22 °C) water was up to 75.5° E in August-September in normal years that was limited up to 76.2° E in pIOD years. The heat budget analysis reveals the decreased contribution of vertical entrainment process to the mixed layer cooling in pIOD years which is almost half of that of normal years in October. The net heat flux term shows warming tendency during May-November with a higher magnitude (+ 0.4 °C day-1) in normal years than pIOD years (+ 0.28 °C day-1). The biological productivity is found to reduce during the pIOD years as the concentration of phytoplankton and zooplankton decreases over the region of coastal upwelling at SWCI. Nitrate concentration in the pIOD years dropped by half during August-September and dropped by an order of magnitude in October as compared to its ambient concentration of 13 μmol L-1 in normal years.

Impact of Indian ocean dipole on the coastal upwelling features off the southwest coast of India

NASA Astrophysics Data System (ADS)

Nigam, Tanuja; Pant, Vimlesh; Prakash, Kumar Ravi

2018-06-01

A three-dimensional regional ocean model is used to examine the impact of positive Indian ocean dipole (pIOD) events on the coastal upwelling features at the southwest coast of India (SWCI). Two model experiments are carried out with different surface boundary conditions that prevailed in the normal and pIOD years from 1982 to 2010. Model experiments demonstrate the weakening of coastal upwelling at the SWCI in the pIOD years. The reduced southward meridional wind stress off the SWCI leads to comparatively lower offshore Ekman transport during August-October in the pIOD years to that in normal years. The suppressed coastal upwelling results in warmer sea surface temperature and deeper thermocline in the pIOD years during June-September. The offshore spatial extent of upwelled colder (< 22 °C) water was up to 75.5° E in August-September in normal years that was limited up to 76.2° E in pIOD years. The heat budget analysis reveals the decreased contribution of vertical entrainment process to the mixed layer cooling in pIOD years which is almost half of that of normal years in October. The net heat flux term shows warming tendency during May-November with a higher magnitude (+ 0.4 °C day-1) in normal years than pIOD years (+ 0.28 °C day-1). The biological productivity is found to reduce during the pIOD years as the concentration of phytoplankton and zooplankton decreases over the region of coastal upwelling at SWCI. Nitrate concentration in the pIOD years dropped by half during August-September and dropped by an order of magnitude in October as compared to its ambient concentration of 13 μmol L-1 in normal years.

Upwelling-Induced Primary Productivity in Coastal Waters of the Black Sea: Impact on Algorithms for Remote Sensing

NASA Technical Reports Server (NTRS)

Goldman, Joel C.; Brink, Kenneth K.; Gawarkiewicz, Glen; Sosik, Heidi M.

1997-01-01

This research program was a collaborative effort to investigate the impact of rapid changes in the water column during coastal upwelling, on biological and optical properties. These properties are important for constructing region or event-specific algorithms for remote sensing of pigment concentration and primary productivity and for comparing these algorithms with those used for the development of large scale maps from ocean color. We successfully achieved the primary objective of this research project which was to study in situ the dynamics of rapid spatial and temporal changes in properties of the water column during, coastal upwelling off the Crimean Coast in the Black Sea. The work was a collaborative effort between a group of biological and physical oceanographers from the Woods Hole Oceanographic Institution and from two oceanographic research institutions in the Crimea, Ukraine, located near the study site, the Marine Hydrophysical Institute (MHI) and the Institute of Biology of the Southern Seas (IBSS). The site was an ideal experimental model, both from a technical and economic standpoint, because of the predictable summer upwelling that occurs in the region and because of the availability of both a ship on call and laboratory and remote sensing facilities at the nearby marine institutes. We used a combination of shipboard measurements and remote sensing to investigate the physical evolution of rapid upwelling events and their impact on photoplankton and water column optical properties. The field work involved a two day cruise for mooring, deployment and a three day baseline survey cruise, followed by an eleven day primary cruise during, a summer upwelling event (anticipated by monitoring local winds and tracked by remote sensing imaging). An MHI ship was outfitted and used for these purposes.

Linking benthic community structure to terrestrial runoff and upwelling in the coral reefs of northeastern Hainan Island

NASA Astrophysics Data System (ADS)

Li, Xiubao; Wang, Daoru; Huang, Hui; Zhang, Jing; Lian, Jiansheng; Yuan, Xiangcheng; Yang, Jianhui; Zhang, Guoseng

2015-04-01

Near-shore coral reefs in northeastern Hainan Island are close to river mouths and aquaculture ponds, and also located at the center of the Qiongdong Upwelling (QDU). However, it is still unclear how terrestrial runoff and upwelling influence the community composition and spatial distribution of the benthos. During three cruises in 2010 and 2011 in Wenchang, northeastern Hainan Island, we determined a subset of environmental parameters in seawater (e.g. temperature, salinity, DO, dissolved inorganic nutrient (DIN), turbidity and transparency) and macroalgal δ15N and investigated the benthic communities (e.g. live coral cover, coral species richness, juvenile coral density, macroalgal cover and coverage of calcified algae) by video transect and visual census techniques at 10 stations (i.e. 1S-6D). The results showed that the QDU has influenced the reef waters in Wenchang. In 2011, the upwelling started in early May, peaked in July and disappeared in September and most upwelling events lasted for 1-2 weeks between May and July. The results also demonstrated that the reef water was nutrient enriched. Stations close to the river mouth and aquaculture ponds had higher levels of DIN and a higher percentage of ammonia in DIN, and there was consistently lower live coral cover, juvenile coral density and higher macroalgal cover. At some stations in this study, live coral cover was negatively correlated with macroalgal cover (i.e. 2S-6D). Live coral cover, species richness, and juvenile coral density all increased with the distance away from the river outlet and decreased with the rise of DIN. These results suggest that terrestrial runoff and upwelling stimulate nutrient enrichment, and that overgrowing macroalgae has an important influence on the coral communities in northeastern Hainan Island.

Influence of basin-scale and mesoscale physical processes on biological productivity in the Bay of Bengal during the summer monsoon

NASA Astrophysics Data System (ADS)

Muraleedharan, K. R.; Jasmine, P.; Achuthankutty, C. T.; Revichandran, C.; Dinesh Kumar, P. K.; Anand, P.; Rejomon, G.

2007-03-01

Physical forcing plays a major role in determining biological processes in the ocean across the full spectrum of spatial and temporal scales. Variability of biological production in the Bay of Bengal (BoB) based on basin-scale and mesoscale physical processes is presented using hydrographic data collected during the peak summer monsoon in July-August, 2003. Three different and spatially varying physical processes were identified in the upper 300 m: (I) anticyclonic warm gyre offshore in the southern Bay; (II) a cyclonic eddy in the northern Bay; and (III) an upwelling region adjacent to the southern coast. In the warm gyre (>28.8 °C), the low salinity (33.5) surface waters contained low concentrations of nutrients. These warm surface waters extended below the euphotic zone, which resulted in an oligotrophic environment with low surface chlorophyll a (0.12 mg m -3), low surface primary production (2.55 mg C m -3 day -1) and low zooplankton biovolume (0.14 ml m -3). In the cyclonic eddy, the elevated isopycnals raised the nutricline upto the surface (NO 3-N > 8.2 μM, PO 4-P > 0.8 μM, SiO 4-Si > 3.5 μM). Despite the system being highly eutrophic, response in the biological activity was low. In the upwelling zone, although the nutrient concentrations were lower compared to the cyclonic eddy, the surface phytoplankton biomass and production were high (Chl a - 0.25 mg m -3, PP - 9.23 mg C m -3 day -1), and mesozooplankton biovolume (1.12 ml m -3) was rich. Normally in oligotrophic, open ocean ecosystems, primary production is based on ‘regenerated’ nutrients, but during episodic events like eddies the ‘production’ switches over to ‘new production’. The switching over from ‘regenerated production’ to ‘new production’ in the open ocean (cyclonic eddy) and establishment of a new phytoplankton community will take longer than in the coastal system (upwelling). Despite the functioning of a cyclonic eddy and upwelling being divergent (transporting of nutrients from deeper waters to surface), the utilization of nutrients leading to enhanced biological production and its transfer to upper trophic levels in the upwelling region imply that the energy transfer from primary production to secondary production (mesozooplankton) is more efficient than in the cyclonic eddy of the open ocean. The results suggest that basin-scale and mesoscale processes influence the abundance and spatial heterogeneity of plankton populations across a wide spatial scale in the BoB. The multifaceted effects of these physical processes on primary productivity thus play a prominent role in structuring of zooplankton communities and could consecutively affect the recruitment of pelagic fisheries.

Data requirements in support of the marine weather service program

NASA Technical Reports Server (NTRS)

Travers, J.; Mccaslin, R. W.; Mull, M.

1972-01-01

Data support activities for the Marine Weather Service Program are outlined. Forecasts, cover anomolous water levels, including sea and swell, surface and breakers, and storm surge. Advisories are also provided for sea ice on the Great Lake and Cook inlet in winter, and in the Bering, Chukchi, and Beaufort Seas in summer. Attempts were made to deal with ocean currents in the Gulf Stream, areas of upwelling, and thermal structure at least down through the mixed layer.

Ocean-ice interaction in the marginal ice zone

NASA Technical Reports Server (NTRS)

Liu, Antony K.; Peng, Chich Y.

1994-01-01

Ocean ice interaction processes in the Marginal Ice Zone (MIZ) by wind, waves, and mesoscale features, such as upwelling and eddies, are studied using ERS-1 Synthetic Aperture Radar (SAR) images and ocean ice interaction model. A sequence of SAR images of the Chukchi Sea MIZ with three days interval are studied for ice edge advance/retreat. Simultaneous current measurements from the northeast Chukchi Sea as well as the Barrow wind record are used to interpret the MIZ dynamics.

Global Ocean Vertical Velocity From a Dynamically Consistent Ocean State Estimate

NASA Astrophysics Data System (ADS)

Liang, Xinfeng; Spall, Michael; Wunsch, Carl

2017-10-01

Estimates of the global ocean vertical velocities (Eulerian, eddy-induced, and residual) from a dynamically consistent and data-constrained ocean state estimate are presented and analyzed. Conventional patterns of vertical velocity, Ekman pumping, appear in the upper ocean, with topographic dominance at depth. Intense and vertically coherent upwelling and downwelling occur in the Southern Ocean, which are likely due to the interaction of the Antarctic Circumpolar Current and large-scale topographic features and are generally canceled out in the conventional zonally averaged results. These "elevators" at high latitudes connect the upper to the deep and abyssal oceans and working together with isopycnal mixing are likely a mechanism, in addition to the formation of deep and abyssal waters, for fast responses of the deep and abyssal oceans to the changing climate. Also, Eulerian and parameterized eddy-induced components are of opposite signs in numerous regions around the global ocean, particularly in the ocean interior away from surface and bottom. Nevertheless, residual vertical velocity is primarily determined by the Eulerian component, and related to winds and large-scale topographic features. The current estimates of vertical velocities can serve as a useful reference for investigating the vertical exchange of ocean properties and tracers, and its complex spatial structure ultimately permits regional tests of basic oceanographic concepts such as Sverdrup balance and coastal upwelling/downwelling.

The pelagic ecosystem in the Northern California Current off Oregon during the 2014-2016 warm anomalies within the context of the past 20 years

NASA Astrophysics Data System (ADS)

Peterson, William T.; Fisher, Jennifer L.; Strub, P. Ted; Du, Xiuning; Risien, Craig; Peterson, Jay; Shaw, C. Tracy

2017-09-01

A warm anomaly in the upper ocean, colloquially named "the Blob," appeared in the Gulf of Alaska during the calm winter of 2013-2014, spread across the northern North Pacific (NP) Ocean, and shifted eastward and onto the Oregon shelf. At least 14 species of copepods occurred which had never been observed in shelf/slope waters off Oregon, some of which are known to have NP Gyre affinities, indicating that the source waters of the coastal "Blob" were likely of both offshore (from the west) and subtropical/tropical origin. The anomalously warm conditions were reduced during strong upwelling in spring 2015 but returned when upwelling weakened in July 2015 and transitioned to downwelling in fall 2015. The extended period of warm conditions resulted in prolonged effects on the ecosystem off central Oregon, lasting at least through 2016. Impacts to the lower trophic levels were unprecedented and include a novel plankton community composition resulting from increased copepod, diatom, and dinoflagellate species richness and increased abundance of dinoflagellates. Additionally, the multiyear warm anomalies were associated with reduced biomass of copepods and euphausiids, high abundance of larvaceans and doliolids (indictors of oligotrophic ocean conditions), and a toxic diatom bloom (Pseudo-nitzschia) throughout the California Current in 2015, thereby changing the composition of the food web that is relied upon by many commercially and ecologically important species.

Sensitivity studies with a coupled ice-ocean model of the marginal ice zone

NASA Technical Reports Server (NTRS)

Roed, L. P.

1983-01-01

An analytical coupled ice-ocean model is considered which is forced by a specified wind stress acting on the open ocean as well as the ice. The analysis supports the conjecture that the upwelling dynamics at ice edges can be understood by means of a simple analytical model. In similarity with coastal problems it is shown that the ice edge upwelling is determined by the net mass flux at the boundaries of the considered region. The model is used to study the sensitivity of the upwelling dynamics in the marginal ice zone to variation in the controlling parameters. These parameters consist of combinations of the drag coefficients used in the parameterization of the stresses on the three interfaces atmosphere-ice, atmosphere-ocean, and ice-ocean. The response is shown to be sensitive to variations in these parameters in that one set of parameters may give upwelling while a slightly different set of parameters may give downwelling.

Mesoscale ocean fronts enhance carbon export due to gravitational sinking and subduction

NASA Astrophysics Data System (ADS)

Stukel, Michael R.; Aluwihare, Lihini I.; Barbeau, Katherine A.; Chekalyuk, Alexander M.; Goericke, Ralf; Miller, Arthur J.; Ohman, Mark D.; Ruacho, Angel; Song, Hajoon; Stephens, Brandon M.; Landry, Michael R.

2017-02-01

Enhanced vertical carbon transport (gravitational sinking and subduction) at mesoscale ocean fronts may explain the demonstrated imbalance of new production and sinking particle export in coastal upwelling ecosystems. Based on flux assessments from 238U:234Th disequilibrium and sediment traps, we found 2 to 3 times higher rates of gravitational particle export near a deep-water front (305 mg Cṡm-2ṡd-1) compared with adjacent water or to mean (nonfrontal) regional conditions. Elevated particle flux at the front was mechanistically linked to Fe-stressed diatoms and high mesozooplankton fecal pellet production. Using a data assimilative regional ocean model fit to measured conditions, we estimate that an additional ˜225 mg Cṡm-2ṡd-1 was exported as subduction of particle-rich water at the front, highlighting a transport mechanism that is not captured by sediment traps and is poorly quantified by most models and in situ measurements. Mesoscale fronts may be responsible for over a quarter of total organic carbon sequestration in the California Current and other coastal upwelling ecosystems.

Mesoscale ocean fronts enhance carbon export due to gravitational sinking and subduction

PubMed Central

Stukel, Michael R.; Aluwihare, Lihini I.; Barbeau, Katherine A.; Chekalyuk, Alexander M.; Goericke, Ralf; Miller, Arthur J.; Ohman, Mark D.; Ruacho, Angel; Song, Hajoon; Stephens, Brandon M.; Landry, Michael R.

2017-01-01

Enhanced vertical carbon transport (gravitational sinking and subduction) at mesoscale ocean fronts may explain the demonstrated imbalance of new production and sinking particle export in coastal upwelling ecosystems. Based on flux assessments from 238U:234Th disequilibrium and sediment traps, we found 2 to 3 times higher rates of gravitational particle export near a deep-water front (305 mg C⋅m−2⋅d−1) compared with adjacent water or to mean (nonfrontal) regional conditions. Elevated particle flux at the front was mechanistically linked to Fe-stressed diatoms and high mesozooplankton fecal pellet production. Using a data assimilative regional ocean model fit to measured conditions, we estimate that an additional ∼225 mg C⋅m−2⋅d−1 was exported as subduction of particle-rich water at the front, highlighting a transport mechanism that is not captured by sediment traps and is poorly quantified by most models and in situ measurements. Mesoscale fronts may be responsible for over a quarter of total organic carbon sequestration in the California Current and other coastal upwelling ecosystems. PMID:28115723

Mantle convection pattern and subcrustal stress field under South America

NASA Technical Reports Server (NTRS)

Liu, H.-S.

1980-01-01

The tectonic, igneous and metallogenic features of South America are discussed in terms of the crustal deformation associated with stresses due to mantle convection as inferred from the high degree harmonics in the geopotential field. The application of Runcorn's model for the laminar viscous flows in the upper mantle to satellite and gravity data results in a convection pattern which reveals the ascending flows between the descending Nazca plate and the overlying South American plate as well as segments of the descending Nazca plate beneath South America. The arc volcanism in South America is shown apparently to be related to the upwelling of high-temperature material induced by the subduction of the Nazca plate, with the South American basin systems associated with downwelling mantle flows. The resulting tensional stress fields are shown to be regions of structural kinship characterized by major concentrations of ore deposits and related to the cordillera, shield and igneous systems and the upward Andean movements. It is suggested that the upwelling convection flows in the upper mantle, coupled with crustal tension, have provided an uplift mechanism which has forced the hydrothermal systems in the basement rocks to the surface.

Characteristics of the Norwegian Coastal Current during Years with High Recruitment of Norwegian Spring Spawning Herring (Clupea harengus L.)

PubMed Central

Skagseth, Øystein; Slotte, Aril; Stenevik, Erling Kåre; Nash, Richard D. M.

2015-01-01

Norwegian Spring Spawning herring (NSSH) Clupea harengus L. spawn on coastal banks along the west coast of Norway. The larvae are generally transported northward in the Norwegian Coastal Current (NCC) with many individuals utilizing nursery grounds in the Barents Sea. The recruitment to this stock is highly variable with a few years having exceptionally good recruitment. The principal causes of recruitment variability of this herring population have been elusive. Here we undertake an event analysis using data between 1948 and 2010 to gain insight into the physical conditions in the NCC that coincide with years of high recruitment. In contrast to a typical year when northerly upwelling winds are prominent during spring, the years with high recruitment coincide with predominantly southwesterly winds and weak upwelling in spring and summer, which lead to an enhanced northward coastal current during the larval drift period. Also in most peak recruitment years, low-salinity anomalies are observed to propagate northward during the spring and summer. It is suggested that consistent southwesterly (downwelling) winds and propagating low-salinity anomalies, both leading to an enhanced northward transport of larvae, are important factors for elevated recruitment. At the same time, these conditions stabilize the coastal waters, possibly leading to enhanced production and improved feeding potential along the drift route to Barents Sea. Further studies on the drivers of early life history mortality can now be undertaken with a better understanding of the physical conditions that prevail during years when elevated recruitment occurs in this herring stock. PMID:26636759

Dynamical consequences of compositional and thermal density stratification beneath spreading centers

NASA Technical Reports Server (NTRS)

Sotin, C.; Parmentier, E. M.

1989-01-01

Dynamical consequences of compositional buoyancy and the combined effects of compositional and thermal buoyancy on mantle flow and crustal production are explored. The results show that for a low enough mantle viscosity, buoyant upwelling can significantly enhance the crustal thickness relative to that which would be produced by plate spreading alone, while for a mantle viscosity of 10 to the 22nd Pa s, upwelling due to plate spreading is dominant and crustal thickness is predicted to be a function of spreading rate. The results indicate that thermal and compositional density variations result in opposing buoyancy forces that can cause time-dependent upwelling.

The Bolivar Channel Ecosystem of the Galapagos Marine Reserve: Energy flow structure and role of keystone groups

NASA Astrophysics Data System (ADS)

Ruiz, Diego J.; Wolff, Matthias

2011-08-01

The Bolivar Channel Ecosystem (BCE) is among the most productive zones in the Galapagos Marine Reserve (GMR). It is exposed to relatively cool, nutrient-rich waters of the Cromwell current, which are brought to the photic zone through topographic upwelling. The BCE is characterized by a heterogeneous rocky reef habitat covered by dense algae beds and inhabited by numerous invertebrate and fish species, which represent the food for higher predators including seals and sharks and exploited fish species. In addition, plankton and detritus based food chains channel large amounts of energy through the complex food web. Important emblematic species of the Galapagos archipelagos reside in this area such as the flightless cormorant, the Galapagos penguin and the marine iguanas. A trophic model of BCE was constructed for the habitats < 30 m depth that fringe the west coast of Isabela and east coast of Fernandina islands covering 14% of the total BCE area (44 km 2). The model integrates data sets from sub tidal ecological monitoring and marine vertebrate population monitoring (2004 to 2008) programs of the Charles Darwin Foundation and consists of 30 compartments, which are trophically linked through a diet matrix. Results reveal that the BCE is a large system in terms of flows (38 695 t km - 2 yr - 1 ) comparable to Peruvian Bay Systems of the Humboldt upwelling system. A very large proportion of energy flows from the primary producers (phytoplankton and macro-algae) to the second level and to the detritus pool. Catches are high (54.3 t km - 2 yr - 1 ) and are mainly derived from the second and third trophic levels (mean TL of catch = 2.45) making the fisheries gross efficiency high (0.3%). The system's degree of development seems rather low as indicated by a P/R ratio of 4.19, a low ascendency (37.4%) and a very low Finn's cycling index (1.29%). This is explained by the system's exposure to irregular changes in oceanographic conditions as related to the EL Niño Southern Oscillation. Most important keystone groups of large relative impact over other system compartments are sharks and marine mammals. In addition, the important role of macro-algae, sea stars and urchins, phytoplankton and barracudas should be emphasized for their great contribution to the trophic flows and biomass of the system.

A Comparison of the Role of Episode Nutrient Supply on Pathways of Carbon in Upwelling Regimes

NASA Technical Reports Server (NTRS)

Carr, M. E.

1997-01-01

Nutrient supply is episode in the ocean even in regions of fairly high and continuous nutrient supply, such as coastal upwelling regimes. The structure of the ecosystem depends on nutrient availability and the different requirements of phytoplankton cells.

Open oceanic productivity changes at mid-latitudes during interglacials and its relation to the Atlantic Meridional Overturning Circulation

NASA Astrophysics Data System (ADS)

Nave, Silvia; Lebreiro, S.; Kissel, C.; Guihou, A.; Figueiredo, M. O.; Silva, T. P.; Michel, E.; Cortijo, E.; Labeyrie, L.; Voelker, A.

2010-05-01

Variations in the interactions between marine ecosystems, thermohaline circulation, external forcing and atmospheric greenhouse gases concentrations are not yet fully represented in detailed models of the glacial-interglacial transitions. Most of the research on past productivity changes has been focused so far on high-productivity areas such as upwelling areas (i.e. equatorial or coastal upwelling areas) even though those regions appraise only a little part of the ocean. Accordingly, the importance of oceanic productivity changes over glacial/interglacial cycles should be better known, as it may also play an important role on the loss of photosynthetically generated carbon as a central mechanism in the global carbon cycle. Its understanding will help quantifying the parameters needed to run comprehensive climate models, and subsequently help to better predict climate change for the near future. A high-resolution study of oceanic productivity, bottom water flow speed, surface and deep-water mass, bottom water ventilation, and terrestrial input changes during two interglacials (Holocene and Marine Isotope Stage [MIS] 5), at an open ocean site approximately 300 km west off Portugal [IMAGES core MD01-2446: 39°03'N, 12°37'W, 3547 m water depth] was conducted within the AMOCINT project (ESF-EUROCORES programme, 06-EuroMARC-FP-008). Even though siliceous productivity is expectedly low for oceanic regions, it shows a robust and consistent pattern with increased values during cold phases of MIS 5, and during the glacial stages 4 and 6 suggesting higher nutrient availability, during these periods. The same pattern is observed for MIS2 and the last deglaciation. The opal record is fully supported by the organic carbon content and to the estimated productivity using foraminifera based FA20 and SIMMAX.28 transfer functions for a near location. The benthic δ13C record suggests less North Atlantic Deep Water (NADW) coincident with periods of higher productivity. The grain-size variations and magnetic properties, suggests stronger/faster bottom currents during cold phases, in agreement with a stronger component of Antarctic sourced Bottom Water (AABW) at the Eastern Atlantic Margin. The probable enhancement of AABW during these periods may also account for a higher preservation of siliceous biogenic particles at the ocean floor sediment/water interface. Given that MD01-2446 is placed far from the continent, productivity records should mainly reflect local conditions. Still, we should not fully discard the preservation of punctual influence of coastal processes derived from upwelling filament plumes at the Estremadura Plateau. Lebreiro et al., 1997 [Paleoceanography, 12, 718-727] reported for a near location, the dominance of pre-upwelling and post-upwelling related foraminifera species during MIS 6 implying less intense or persistent upwelling during MIS 6 than MIS 4. On the contrary, opal and organic carbon data reveals a clear increase in productivity also during MIS 6, reinforcing the idea that productivity variations are likely related to open ocean conditions and therefore, nutrients availability associated to the Atlantic Meridional Oceanic Circulation.

Plants as Indicators of Past and Present Zones of Upwelling Soil CO2 at the ZERT Facility

NASA Astrophysics Data System (ADS)

Apple, M. E.; Sharma, B.; Zhou, X.; Shaw, J. A.; Dobeck, L.; Cunnningham, A.; Spangler, L.; ZERT Team

2011-12-01

By their very nature, photosynthetic plants are sensitive and responsive to CO2, which they fix during the Calvin-Benson cycle. Responses of plants to CO2 are valuable tools in the surface detection of upwelling and leaking CO2 from carbon sequestration fields. Plants exposed to upwelling CO2 rapidly exhibit signs of stress such as changes in stomatal conductance, hyperspectral signatures, pigmentation, and viability (Lakkaraju et al. 2010; Male et al. 2010). The Zero Emission Research and Technology (ZERT) site in Bozeman, MT is an experimental facility for surface detection of CO2 where 0.15 ton/day of CO2 was released (7/19- 8/15/2010, and 7/18 - 8/15/2011) from a 100m horizontal injection well, (HIW), 1.5 m underground with deliberate leaks of CO2 at intervals, and from a vertical injector, (VIW), (6/3-6/24/2010). Soil CO2 concentrations reached 16%. Plants at ZERT include Taraxacum officinale (Dandelion), Dactylis glomerata (Orchard Grass), Poa pratensis, (Kentucky Bluegrass), Phleum pratense (Timothy), Bromus japonicus (Japanese Brome), Medicago sativa (Alfalfa) and Cirsium arvense (Canadian Thistle). Dandelion leaves above the zones of upwelling CO2 at the HIW and the VIW changed color from green to reddish-purple (indicative of an increase in anthocyanins) to brown as they senesced within two weeks of CO2 injection. Their increased stomatal conductance along with their extensive surface area combined to make water loss occur quickly following injection of CO2. Xeromorphic grass leaves were not as profoundly affected, although they did exhibit changes in stomatal conductance, accelerated loss of chlorophyll beyond what would normally occur with seasonal senescence, and altered hyperspectral signatures. Within two weeks of CO2 injection at the HIW and the VIW, hot spots formed, which are circular zones of visible leaf senescence that appear at zones of upwelling CO2. The hot spots became more pronounced as the CO2 injection continued, and were detectable until obscured by snow in the fall and winter. Residual hot spots were visible in the spring after a summer CO2 injection. At both the HIW and the VIW, dandelions were less abundant, if not scarce, in the hot spots when quantified the next year. We mounted a Star-Dot web camera on a scaffold, from which the camera photographs the area each day at noon. The camera remains in place year round and obtains images of the current and residual hot spots, and the growth, color changes, and senescence of the plants. We also quantified percent coverage of plant species along the HIW and the VIW. At the VIW, which received CO2 in 2010 but not in 2011, the site of the 2010 hot spot was detectable in 2011 as a scarcity of dandelion leaves. Therefore, previous, or antecedent, conditions influenced the distribution of species at the VIW and do not depend on continuous injection of CO2. Sudden and long-term shifts in species composition have important ecological implications and may serve as a means of surface detection of upwelling CO2.

Seasonal Synechococcus and Thaumarchaeal population dynamics examined with high resolution with remote in situ instrumentation

PubMed Central

Robidart, Julie C; Preston, Christina M; Paerl, Ryan W; Turk, Kendra A; Mosier, Annika C; Francis, Christopher A; Scholin, Christopher A; Zehr, Jonathan P

2012-01-01

Monterey Bay, CA is an Eastern boundary upwelling system that is nitrogen limited much of the year. In order to resolve population dynamics of microorganisms important for nutrient cycling in this region, we deployed the Environmental Sample Processor with quantitative PCR assays targeting both ribosomal RNA genes and functional genes for subclades of cyanobacteria (Synechococcus) and ammonia-oxidizing Archaea (Thaumarchaeota) populations. Results showed a strong correlation between Thaumarchaea abundances and nitrate during the spring upwelling but not the fall sampling period. In relatively stratified fall waters, the Thaumarchaeota community reached higher numbers than in the spring, and an unexpected positive correlation with chlorophyll concentration was observed. Further, we detected drops in Synechococcus abundance that occurred on short (that is, daily) time scales. Upwelling intensity and blooms of eukaryotic phytoplankton strongly influenced Synechococcus distributions in the spring and fall, revealing what appear to be the environmental limitations of Synechococcus populations in this region. Each of these findings has implications for Monterey Bay biogeochemistry. High-resolution sampling provides a better-resolved framework within which to observe changes in the plankton community. We conclude that controls on these ecosystems change on smaller scales than are routinely assessed, and that more predictable trends will be uncovered if they are evaluated within seasonal (monthly), rather than on annual or interannual scales. PMID:21975596

Connecting pigment composition and dissolved trace elements to phytoplankton population in the southern Benguela Upwelling zone (St. Helena Bay)

NASA Astrophysics Data System (ADS)

Das, Supriyo Kumar; Routh, Joyanto; Roychoudhury, Alakendra N.; Veldhuis, Marcel J. W.; Ismail, Hassan E.

2017-12-01

Rich in upwelled nutrients, the Southern Benguela is one of the most productive ecosystems in the world ocean. However, despite its ecological significance the role of trace elements influencing phytoplankton population in the Southern Benguela Upwelling System (SBUS) has not been thoroughly investigated. Here, we report pigment composition, macronutrients (nitrate, phosphate and silicate) and concentrations of dissolved Cd, Co, Fe and Zn during late austral summer and winter seasons in 2004 to understand the relationship between the selected trace elements and phytoplankton biomass in St. Helena Bay (SHB), which falls within the southern boundary of the SBUS. Chlorophyll a concentrations indicate higher phytoplankton biomass associated with high primary production during late summer in SHB where high diatom population is inferred from the presence of fucoxanthin. Diminished phytoplankton biomass and a shift from diatoms to dinoflagellates as the dominant phytoplankton taxa are indicated by diagnostic pigments during late winter. Dissolved trace elements (Cd, Co and Zn) and macronutrients play a significant role in phytoplankton biomass, and their distribution is affected by biological uptake and export of trace elements. Continuous uptake of Zn by diatoms may cause an onset of Zn depletion leading to a period of extended diatom proliferation during late summer. Furthermore, the transition from diatom to dinoflagellate dominated phytoplankton population is most likely facilitated by depletion of trace elements (Cd and Co) in the water column.

Community response of zooplankton to oceanographic changes (2002-2012) in the central/southern upwelling system of Chile

NASA Astrophysics Data System (ADS)

Medellín-Mora, Johanna; Escribano, Ruben; Schneider, Wolfgang

2016-03-01

A 10-year time series (2002-2012) at Station 18 off central/southern Chile allowed us to study variations in zooplankton along with interannual variability and trends in oceanographic conditions. We used an automated analysis program (ZooImage) to assess changes in the mesozooplankton size structure and the composition of the taxa throughout the entire community. Oceanographic conditions changed over the decade: the water column became less stratified, more saline, and colder; the mixed layer deepened; and the oxygen minimum zone became shallower during the second half of the time series (2008-2012) in comparison with the first period (2002-2007). Both the size structure and composition of the zooplankton were significantly associated with oceanographic changes. Taxonomic and size diversity of the zooplankton community increased to the more recent period. For the second period, small sized copepods (<1 mm) decreased in abundance, being replaced by larger sized (>1.5 mm) and medium size copepods (1-1.5 mm), whereas euphausiids, decapod larvae, appendicularian and ostracods increased their abundance during the second period. These findings indicated that the zooplankton community structure in this eastern boundary ecosystem was strongly influenced by variability of the upwelling process. Thus, climate-induced forcing of upwelling trends can alter the zooplankton community in this highly productive region with potential consequences for the ecosystem food web.

Why coastal upwelling is expected to increase along the western Iberian Peninsula over the next century?

PubMed

Sousa, Magda Catarina; deCastro, Maite; Alvarez, Ines; Gomez-Gesteira, Moncho; Dias, João Miguel

2017-08-15

Former studies about coastal upwelling along the Western Iberian Peninsula (WIP) using historical data indicated contradictory results, showing either its strengthening or reduction, while previous studies using Global Climate Models (GCMs) indicated that global warming is likely to intensify this phenomenon although predicting different rates and not justifying the patterns found. Taking advantage of the recent high spatial resolution Regional Climate Models (RCMs) projections from EURO-CORDEX project (Representative Concentration Pathway, RCP 8.5), detailed higher accuracy estimations of the spatio-temporal trends of Upwelling Index (UI) along the WIP coast were performed in this study, integrating the coastal mesoscale effects within the framework of climate change. Additionally, this research brings new insights about the origin of the WIP coastal upwelling intensification over the next century. These new projections clarified the upwelling strengthening rates predicted along the coast of the WIP from 2006 to 2099 revealing more prominent changes in the northern limit of the region (25-30m 3 s -1 km -1 per decade between 41.5 and 42.5°N). Trends observed at high latitudes of the region were found to be induced by the displacement of the Azores High, which will intensify (0.03hPa per decade) and drift northeastward (10km per decade) during the 21st century. Copyright © 2017 Elsevier B.V. All rights reserved.

Fine-scale variability of isopycnal salinity in the California Current System

NASA Astrophysics Data System (ADS)

Itoh, Sachihiko; Rudnick, Daniel L.

2017-09-01

This paper examines the fine-scale structure and seasonal fluctuations of the isopycnal salinity of the California Current System from 2007 to 2013 using temperature and salinity profiles obtained from a series of underwater glider surveys. The seasonal mean distributions of the spectral power of the isopycnal salinity gradient averaged over submesoscale (12-30 km) and mesoscale (30-60 km) ranges along three survey lines off Monterey Bay, Point Conception, and Dana Point were obtained from 298 transects. The mesoscale and submesoscale variance increased as coastal upwelling caused the isopycnal salinity gradient to steepen. Areas of elevated variance were clearly observed around the salinity front during the summer then spread offshore through the fall and winter. The high fine-scale variances were observed typically above 25.8 kg m-3 and decreased with depth to a minimum at around 26.3 kg m-3. The mean spectral slope of the isopycnal salinity gradient with respect to wavenumber was 0.19 ± 0.27 over the horizontal scale of 12-60 km, and 31%-35% of the spectra had significantly positive slopes. In contrast, the spectral slope over 12-30 km was mostly flat, with mean values of -0.025 ± 0.32. An increase in submesoscale variability accompanying the steepening of the spectral slope was often observed in inshore areas; e.g., off Monterey Bay in winter, where a sharp front developed between the California Current and the California Under Current, and the lower layers of the Southern California Bight, where vigorous interaction between a synoptic current and bottom topography is to be expected.

Evaluation of the ecological integrity and ecosystem health of three benthic networks influenced by coastal upwelling in the northern Chile

EPA Science Inventory

The ecological health of ecosystems relates to the maintenance or restoration of optimal system function when confronted with a disturbance. A healthy ecosystem is a prerequisite for ecological sustainability. Ecological integrity has been defined as an emergent property of ecosy...

On the "hidden" phytoplankton blooms on Australia's southern shelves

NASA Astrophysics Data System (ADS)

Kämpf, Jochen; Kavi, Ankit

2017-02-01

Phytoplankton blooms on Australia's southern shelves are revisited using satellite-derived monthly data of chlorophyll a concentrations for the period 2003-2015. It is known that the region hosts a seasonal coastal upwelling system that develops in austral summer (January-March) with chlorophyll a concentrations of >2 mg/m3. While this summer upwelling is spatially limited to a few hot spots, here we show that widespread phytoplankton blooms of moderate ( 1 mg/m3) chlorophyll a concentrations develop during autumn and early winter on most of Australia's extensive southern shelves—from the vast shelves of the Great Australian Bight (GAB) in the west to Bass Strait in the east. This surprising finding disproves the widespread belief that shelf waters of the GAB are generally oligotrophic and may explain the relatively high abundance of both forage fish (sardines) and upper trophic-level predators (e.g., tuna and whales) in the region.

Effect of atmospheric scattering and surface reflection on upwelling solar radiation

NASA Technical Reports Server (NTRS)

Suttles, J. T.; Barkstrom, B. R.; Tiwari, S. N.

1981-01-01

A study is presented of the solar radiation transfer in the complete earth-atmosphere system, and numerical results are compared with satellite data obtained during the Earth Radiation Budget Experiment on Nimbus 6, in August, 1975. Emphasis is placed on the upwelling radiance distribution at the top of the atmosphere, assumed to be at 50 km. The numerical technique is based on the finite difference method, which includes azimuth and spectral variations for the entire solar wavelength range. Detailed solar properties, atmospheric physical properties, and optical properties are used. However, since the property descriptions are based on a trade-off between accuracy and computational realities, aerosol and cloud optical properties are treated with simple approximations. The radiative transfer model is in good agreement with the satellite radiance observations. The method provides a valuable tool in analyzing satellite- and ground-based radiation budget measurements and in designing instrumentation.

Abyssal Upwelling in Mid-Ocean Ridge Fracture Zones

NASA Astrophysics Data System (ADS)

Clément, Louis; Thurnherr, Andreas M.

2018-03-01

Turbulence in the abyssal ocean plays a fundamental role in the climate system by sustaining the deepest branch of the overturning circulation. Over the western flank of the Mid-Atlantic Ridge in the South Atlantic, previously observed bottom-intensified and tidally modulated mixing of abyssal waters appears to imply a counterintuitive densification of deep and bottom waters. Here we show that inside fracture zones, however, turbulence is elevated away from the seafloor because of intensified downward propagating near-inertial wave energy, which decays below a subinertial shear maximum. Ray-tracing simulations predict a decay of wave energy subsequent to wave-mean flow interactions. The hypothesized wave-mean flow interactions drive a deep flow toward lighter densities of up to 0.6 Sv over the mid-ocean ridge flank in the Brazil Basin, and the same process may also cause upwelling of abyssal waters in other ocean basins with mid-ocean ridges with fracture zones.